Acs0411 Mediastinal Procedures


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Acs0411 Mediastinal Procedures

  1. 1. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 1 11 MEDIASTINAL PROCEDURES Joseph B. Shrager, M.D., F.A.C.S., and Vivek Patel, M.B.B.S. Procedures for Lesions of the Anterior Mediastinum thymoma or thymic hyperplasia—in 80% to 90% of cases. Thy- More than half of all mediastinal masses arise from the anteri- moma may also be associated with pure red cell aplasia, agamma- or compartment. Most primary malignancies of the mediastinum globulinemia, systemic lupus erythematosus, and various auto- also develop in the anterior mediastinum. Because of the narrow- immune disorders. The presence of any of these associated syn- ness of the space that makes up the thoracic inlet, as well as the dromes essentially clinches the diagnosis of thymoma. Autoanti- presence of the trachea and esophagus traversing this region, ante- bodies to the acetylcholine receptor (anti-AChR antibodies) rior mediastinal masses become symptomatic earlier than their should be measured: their presence is diagnostic of MG, and they counterparts in other anatomic spaces of the mediastinum.Where- are found in nearly 60% of patients who have thymoma without as adults with masses of the middle or posterior mediastinum usu- neurologic symptoms.3 Once the diagnosis of thymoma has been ally report no significant symptoms, more than 50% of patients made, the goal is to proceed to direct resection without prelimi- with anterior mediastinal masses present with chest pain, fever, nary biopsy; these tumors have a predilection for local recurrence cough, dyspnea, dysphagia, or vascular obstruction. Thymic neo- once the capsule has been violated. plasms and lymphoma, the two most common masses in the ante- The majority of germ cell tumors, whether malignant or be- rior mediastinum, may have systemic manifestations (e.g., weak- ness associated with myasthenia gravis [MG] or symptoms asso- ciated with International Working Formulation [IWF] group B Table 1 Differential Diagnosis of Anterior lymphoma). Mediastinal Mass In what follows, we focus on surgical approaches to diagnosis and treatment of the more common neoplasms of the anterior Thyroid mediastinum, including thymic tumors, lymphomas, and germ cell Substernal goiter tumors. Embryologic anomalies and neoplasms arising from nor- Ectopic thyroid tissue mal structures in this region broaden the differential diagnosis [see Thymus Table 1]. Finally, we address thymectomy for MG, a procedure that Thymic hyperplasia is frequently performed even in the absence of neoplastic disease. Thymoma Thymic carcinoma PREOPERATIVE EVALUATION Thymic carcinoid Thymic small cell carcinoma In a patient with an anterior mediastinal mass, it is frequently Thymic cyst possible to make a strong provisional diagnosis of the tumor type Thymolipoma on the basis of clinical evaluation and diagnostic imaging.1 As Teratoma noted (see above), the presence of systemic manifestations may be Mature teratoma helpful. Physical examination must include examination of pe- Neoplastic conditions Immature teratoma ripheral lymph node groups and testes. Computed tomography Teratoma with malignant component yields valuable information about the anatomic location of the Lymphoma Ectopic parathyroid with adenoma tumor, its characteristics (i.e., fatty, solid, or cystic), and its degree Germ cell tumors of invasiveness (if any) [see Figure 1]. Occasionally, magnetic reso- Seminoma nance imaging provides useful additional information about the Nonseminoma obliteration of normal tissue planes. Yolk sac tumor Lymphoma is the most likely diagnosis in persons younger than Embryonal carcinoma 40 years, and the presence of IWF group B symptoms further rais- Choriocarcinoma es the level of suspicion.The presence of palpable remote adenop- Hemangioma athy or an elevated serum lactic dehydrogenase (LDH) level is also Lipoma suggestive.2 When peripheral nodes are palpable, the diagnosis Liposarcoma Fibroma may be most easily obtained by excising one of them. Patients with Fibrosarcoma suspected lymphoma who have an isolated anterior mediastinal Cervicomediastinal hygroma mass should undergo core-needle biopsy or a Chamberlain proce- dure (anterior mediastinotomy), depending on the pathologists’ Acute descending necrotizing mediastinitis Infectious conditions level of comfort with classifying lymphoma on the basis of small Subacute mediastinitis specimens at one’s institution. Resection of lymphoma is not indi- Aneurysm of aortic arch with projection in anterior cated; it may be avoided by performing a diagnostic biopsy when- mediastinum ever lymphoma is suspected. Innominate vein aneurysm Unlike lymphomas, thymic neoplasms are uncommon before Vascular conditions Superior vena cava aneurysm the fourth decade of life.Thymoma [see Figure 1a] may be associ- Dilation of superior vena cava (with anomalous pulmonary venous return) ated with any of several paraneoplastic syndromes. MG occurs in Persistent left superior vena cava conjunction with a pathologic condition of the thymus—either
  2. 2. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 2 a or mediastinal mass is not a simple one. Routine biopsy should be avoided, not only because of the cost and the unnecessary mor- bidity but also because of the risk that biopsy may spread thymo- ma.The choice to proceed with biopsy should be made according to which tumor type is believed to be most likely on the basis of the diagnostic workup. Well-encapsulated lesions that are believed not to represent lymphoma are resected, without a preceding biopsy, for both diag- nosis and treatment. Neoplasms that commonly fall into this cat- egory include noninvasive thymomas, mature teratomas, mes- enchymal tumors, and, occasionally, benign cysts. Patients with MG should be offered thymectomy, whether they have a thymic mass or not. When lymphoma is suspected, biopsy is required. The tech- nique employed should be minimally invasive while still permit- ting the acquisition of a sufficient tissue sample. CT-guided core needle biopsy may be attempted, but frequently, this technique b does not provide enough tissue for the analyses required to classi- fy the tumor.7,8 For anterior mediastinal masses that appear to be locally inva- sive or frankly unresectable, biopsy is also preferable to immedi- ate resection. Such lesions may represent aggressive thymomas that may benefit from neoadjuvant treatment, malignant germ cell tumors, or other rare disease processes. Once the decision has been made to proceed with biopsy rather than resection, selection of a biopsy approach is based on anatomic considerations and patient factors. BIOPSY OF ANTERIOR MEDIASTINAL MASS Chamberlain Approach Anterior parasternal mediastinotomy (the Chamberlain proce- dure) is favored by most surgeons for biopsy of lesions in the ante- rior mediastinum and the aortopulmonary window. It is usually Figure 1 (a) CT scan shows a well-encapsulated anterior medi- done under general anesthesia, though local anesthesia may be astinal mass—a thymoma. (b) CT scan shows a benign teratoma of the anterior mediastinum; calcification and varying tissue used instead, and it does not require single-lung ventilation. This densities may be seen. operation affords good exposure and allows generous biopsy spec- imens to be taken, and it can be performed as an outpatient procedure. nign, are diagnosed in the second or third decade of life. Benign teratomas are usually well encapsulated, with frequent recapitula- Operative technique Step 1: initial incision. A 5 cm trans- tion of one or more tissue elements seen on radiography.4 The verse incision is made over the second costal cartilage on the side to appearance of the lesions on CT is often diagnostic [see Figure 1b]. be operated on (the second cartilage is identified by its continuity Surgical extirpation is the mainstay of treatment for these mature with the sternal angle).The pectoralis major is separated in a direc- germ cell tumors, and biopsy is not indicated. Malignant germ tion parallel to the direction of its fibers, and the cartilage is resect- cell tumors, on the other hand, are treated with primary che- ed in a subperichondrial plane [see Figure 2]. Leaving perichondri- motherapy, radiotherapy, or both; when suspected, they should um behind facilitates postoperative regrowth of the cartilage. undergo biopsy rather than proceed directly to resection. Characteristic serum tumor markers, including β–human chori- Step 2: dissection and exposure. The posterior perichondrium is onic gonadotropin (β-hCG) and alpha-fetoprotein (AFP), are incised, and the parietal pleura is bluntly dissected laterally with a elaborated by most malignant germ cell neoplasms but are not peanut sponge; this affords entry into the mediastinal fat and found in benign germ cell tumors.5 Elevation of the AFP level direct access to the tumor mass. Almost invariably, the internal beyond 500 ng/ml is considered diagnostic of a nonseminomatous mammary vessels can be mobilized medially and preserved, but if component in a malignant germ cell tumor and is usually associ- necessary, they may be ligated to improve exposure. ated with a concomitant increase in serum β-hCG levels.6 In the absence of any marked elevation in the AFP or β-hCG level, Step 3: biopsy. A generous wedge-shaped portion of the mass is percutaneous needle biopsy usually suffices to establish the excised with a scalpel. Frozen-section examination is then per- diagnosis. formed to confirm that diagnostic tissue has been obtained. It is important to remember to request that flow cytometry be per- OPERATIVE PLANNING formed on the specimen. Biopsy versus Resection Step 4: closure. The posterior perichondrium is reapproximated, Clearly, the decision whether to perform a biopsy of an anteri- followed by the pectoralis major, the subcutaneous fat, and the skin.
  3. 3. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 3 R2 Figure 2 Biopsy of anterior mediastinal mass: Chamberlain approach. Depicted are incision and subperichondrial resec- tion of the second costal cartilage. Troubleshooting If the pleura was entered, a red rubber space for evidence of tumor dissemination. Robot-assisted thora- catheter is used to evacuate the pleural space as the lung is inflat- coscopic procedures for anterior mediastinal masses have also ed with a large positive pressure breath, and the catheter is with- been described,10 but their availability does not eliminate the drawn through the layers of closure. A small postoperative pneu- major objection to transpleural approaches to mediastinal masses— mothorax is almost always attributable to residual air rather than namely, the possibility of spreading a disease that had been con- to an ongoing air leak. tained within the mediastinum into the pleural space. Sometimes, the tumors are fairly vascular and bleed moderate- RESECTION OF ANTERIOR MEDIASTINAL MASS ly after biopsy is performed. This bleeding can always be con- trolled with electrocauterization. We often leave an absorbable hemostatic agent in place as well. Operative Planning The most frequent indications for resection (as opposed to Transcervical Approach biopsy) of an anterior mediastinal mass are (1) thymoma and (2) As an alternative to the Chamberlain procedure, a mass of the thymectomy for MG. The principles underlying thymoma resec- anterior mediastinum may be approached for biopsy through a tion can be applied to resection of other, rarer anterior mediasti- cervical incision, exactly as in a transcervical thymectomy [see nal masses.The first successful resection of a thymic mass for MG Resection of Anterior Mediastinal Mass, Transcervical Approach, was described in 1939.11 Since the introduction of transcervical below]. The use of a Cooper thymectomy retractor (Pilling Com- thymectomy (TCT), there has been ongoing debate regarding the pany, Fort Washington, Pennsylvania), which elevates the sternum, optimal method for thymectomy in patients with nonthymoma- affords excellent exposure of the anterior mediastinum and some- tous MG. There is little debate, however, regarding the optimal times allows direct examination to ascertain the invasiveness of an approach to resection of anterior mediastinal malignancies. otherwise uncertain mass. In most cases, general anesthesia is For all primary invasive masses of the anterior mediastinum— required, but transcervical biopsy can be performed as an outpa- including invasive thymomas, malignant germ cell tumors (after tient procedure.We have used this technique at our institution and systemic treatment), thymic carcinomas, and other, less common have achieved results comparable to those of anterior mediasti- malignancies—the most important prognostic factor is complete notomy.9 Proper performance of this procedure does, however, resection. Accordingly, the operative approach must be selected require a level of experience with the technique that is not widely with an eye to providing optimal exposure. There is little doubt available. that a full median sternotomy is ideal in this regard. However, a less than full sternotomy is a reasonable choice for small (< 3 cm) Video-Assisted Thoracic Surgery noninvasive thymomas or other noninvasive mediastinal tumors Video-assisted thoracic surgery (VATS) has been applied to (e.g., mature teratomas), particularly when the diagnosis of thy- diagnostic biopsy [see 4:10 Video-Assisted Thoracic Surgery], but moma is in doubt before operation. In such situations, we usually VATS biopsy procedures are not widely employed in the anterior begin with TCT,12 but we do not hesitate to convert to a ster- mediastinum. The necessity of single-lung ventilation adds a level notomy if unexpected invasion is identified. Some surgeons have of complexity to the procedure beyond what is required for the employed a partial upper sternotomy in these settings; however, Chamberlain procedure or the transcervical approach. Further- this approach limits exposure, and we do not believe that it actu- more, intercostal incisions are frequently more painful than trans- ally reduces morbidity in comparison with a full sternotomy. cervical incisions or anterior mediastinotomies. VATS does have En bloc resection of malignancies is mandatory, and resection certain advantages that may be of value in individual cases, such of adjacent serosal membranes (including pleura or pericardium) as the capacity to provide simultaneous access to other compart- is required if there is any suggestion of attachment during the ments of the mediastinum and the ability to evaluate the pleural operation. Resection of adjacent lung parenchyma is not uncom-
  4. 4. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 4 are not remarkably different from those after TCT, which is much less invasive. Because we do not personally perform the maximal- ly invasive procedure, we do not describe it in this chapter. Median Sternotomy Approach As noted (see above), the standard approach to masses of the anterior mediastinum is via a median sternotomy. Resection of a thymoma of the anterior mediastinum is performed as follows. Operative technique Step 1: initial incision and exposure. The patient is placed in the supine position and intubated with a single-lumen tube. If direct extension to the lung is considered a possibility, a double-lumen tube is placed. The skin incision typi- cally extends from 2 cm below the jugular notch to the xiphister- nal junction; however, depending on the extent of the expected pathologic condition, the incision may be shortened further and the full sternum divided by reaching beneath skin flaps. Finger dis- section is performed beneath the sternum to rule out tumor inva- sion into the posterior sternal table. If the posterior sternal table is Figure 3 Resection of anterior mediastinal mass: median ster- clear, the sternum is divided, hemostasis is achieved, and the edges notomy approach. Intraoperative photo shows dissection of the are separated with a sternal retractor. right inferior thymic pole and associated mediastinal fat. Step 2: determination of resectability. The anterior mediastinum is inspected, the mass is visually identified, and an initial assessment mon, and resection of the great vessels has been performed with of resectability is undertaken. both technical success and good long-term survival. All great ves- sels resected must be reconstructed, with the exception of the innominate vein, which may be ligated with little deleterious effect. Every effort should be made to preserve the phrenic nerves: dam- age to even one of these nerves can be disastrous in an already weakened myasthenia patient. In a patient with a malignancy, however, one phrenic nerve may be sacrificed if tumor invasion necessitates this step, provided that the patient’s preoperative res- piratory status is acceptable and curative resection is likely. In cases of thymectomy for advanced MG, every effort must be made to optimize the patient’s condition preoperatively. To this end, a multidisciplinary approach that includes a neurologist and, possibly, a pulmonologist is necessary. If the disease does not sta- bilize with medication (e.g., pyridostigmine, steroids, or intra- venous γ-globulin), preoperative plasmapheresis may be required. The question of which MG patients should be offered thymecto- my is, at best, difficult to answer. Most studies have found the impact of thymectomy to be greater if it is performed early. Accordingly, our practice is to offer TCT sooner in the course of the disease rather than later; however, we will perform the proce- dure at any stage, from ocular-only disease to severe, generalized weakness. Because TCT is associated with minimal morbidity, requires only a small incision, and can generally be done as an out- patient procedure, it is a very attractive option for patients with milder disease. At the same time, it is also more easily tolerated by patients with severe disease than a median sternotomy is. An approach to thymectomy for MG that is favored by a few surgeons is so-called maximal transsternal-transcervical thymic resection, which combines a median sternotomy with an addition- al neck incision to provide wide access to all areas where thymic tis- sue has been identified. The rationale for such extensive exposure is the observation that thymic tissue may reside in several extrathymic locations. Proponents of the maximal approach argue that if thymectomy for MG is to provide optimal benefit, it should include removal of all of this extraglandular thymic tissue. This Figure 4 Resection of anterior mediastinal mass: median ster- approach has never been compared with TCT in a randomized notomy approach. View from feet shows the thymus and tumor trial, but in our view, most of the available data suggest that remis- mobilized off the innominate vein. The entire right thymus (both sion rates after maximal transsternal-transcervical thymic resection the upper and the lower pole) has been fully mobilized.
  5. 5. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 5 The arteries supplying the thymus, arising laterally via branch- es from the internal mammary vessels, are ligated and divided as they are encountered. Care must be taken to stay away from the phrenic nerves while controlling the arterial blood supply. Step 5: mobilization of superior poles of thymus. Dissection is then continued in the neck, where the two cervical extensions are iso- lated by means of gentle traction and blunt dissection and fol- lowed until they trail off into the thyrothymic ligament. This liga- ment is clamped, divided, and ligated superiorly at a point where only a small blood vessel is present and no visible glandular tissue remains. Step 6: dissection of thymus from innominate vein. The cervical poles are followed down over the innominate vein. Sharp dissec- tion is continued onto the surface of the vein, and the two to five Figure 5 Resection of anterior mediastinal mass: median ster- veins draining the gland into the innominate vein are ligated and notomy approach. Shown is the resected thymoma specimen. divided [see Figure 4]. Step 7: removal of specimen. Once the body of the thymus has been freed from the innominate vein, the H-shaped gland and the Step 3: mobilization of inferior poles of thymus. Dissection of the associated mass are removed [see Figure 5]. If the clean plane thymus begins at the caudad aspect, with the inferior poles mobi- between the mass and the underlying pericardium—a plane nor- lized first from the underlying pericardium through electrocautery mally composed of fine, filmy adhesions—is at all compromised, dissection. It is difficult to determine by visual means precisely one should not hesitate to resect a portion of the pericardium en where thymic tissue merges into simple mediastinal fat; accord- bloc with the specimen, with care taken to maintain a gross mar- ingly, to ensure complete resection of the thymus, all fatty tissue gin of at least 2 cm at all times. between the phrenic nerves and down to the level of the dia- phragm is removed with the specimen.The mediastinal pleura, to Step 8: closure. Two pleural drains that traverse the mediasti- which this fatty and thymic tissue tends to be adherent, is also num and reach the apex of each hemithorax are placed, and the taken with the specimen [see Figure 3]. sternum and the soft tissues are reapproximated in layers. Step 4: continuation of dissection cephalad. As dissection proceeds Troubleshooting If invasion of great vessels is considered a cephalad, the phrenic nerves are identified and followed along possibility before the start of the operation, the groin should be their entire path up to the point where they course beneath the prepared and draped into the field to provide access for cardiopul- innominate vein. Sharp dissection often must be carried very close monary bypass if needed. Giant anterior mediastinal masses may to the nerves to secure an adequate tumor margin. It is advisable necessitate extension of a partial median sternotomy incision into to clip small vessels near the nerve before dividing them, so as to an ipsilateral intercostal space (usually the fourth space). Such prevent irritating bleeding, which can be difficult to control with- extension may be achieved by making an ipsilateral incision in the out compromising the nerve. neck along the anterior border of the sternocleidomastoid muscle and making a submammary skin incision continuous with the inci- sion over the sternum (a hemiclamshell incision) [see Figure 6]. Transcervical Approach Although the transcervical approach to thymic resection was the first one used in the early 1900s, it fell into disuse during the mid- dle of the 20th century, when the median sternotomy approach became feasible. During the past 20 years, however, there has been a resurgence of interest in TCT. Today,TCT is used primarily for thymectomy in the setting of MG, though, as noted (see above), a transcervical approach can be useful for biopsy or resection of other anterior mediastinal processes as well. Proponents of TCT have published data establishing that complete remission rates from MG after so-called extended TCT using the sternum-lifting Cooper retractor13 are virtually equivalent to remission rates after the more invasive approaches.14,15 Because TCT is an outpatient procedure, hospital stay and operative recovery are certainly dra- matically shorter than after thymectomy by sternotomy. TCT should be employed very cautiously in cases in which a neoplasm is suspected or proved on the basis of preoperative stud- Figure 6 Resection of anterior mediastinal mass: median ster- ies or is identified during the course of intraoperative exploration. notomy approach. Hemiclamshell incision provides exposure to Because thymoma is often an indolent tumor, with recurrence masses located at the thoracic apex. developing many years after resection, long-term follow-up stud-
  6. 6. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 6 ies are required before TCT can be firmly recommended for treat- ment of even small thymomas. On the other hand, it is likely that surgeons who have extensive experience with TCT can safely resect small (< 3 cm) thymomas via this approach without risking tumor spillage or incomplete resection. Operative technique Step 1: initial incision and exposure. The patient is placed on the operating table in the supine position, with the head supported by a foam doughnut and an inflatable bag placed horizontally beneath the scapulae. The bag is inflated until the cervical spine is maximally extended. It is important that the top of the patient’s head be all the way up to the edge of the table, so that the surgeon can easily reach all areas of the medi- astinum from a seated position at the head. A 5 to 6 cm curvilinear incision is made about 2 cm superior to the jugular notch and extending about 1 cm above each clavicular head [see Figure 7]. Electrocautery dissection is continued through the platysma, and subplatysmal flaps are elevated.The strap mus- cles are separated in the midline, and the interclavicular ligament is divided. Separating a small portion of the attachment of each sternocleidomastoid muscle from the corresponding clavicular head Figure 7 Resection of anterior mediastinal mass: transcervical approach. Shown is the location of the skin incision for TCT in allows the sternum to be elevated somewhat higher, thereby im- relation to the sternal notch and the heads of the clavicles. proving exposure. Step 2: mobilization of superior poles of thymus. The superior Step 6: dissection of posterior aspect of thymus. Once the thymus is poles of the thymus are located (usually on the left side first) by freed from the innominate vein, dissection of the posterior aspect means of gentle blunt dissection beneath the strap muscles. After of the gland must be continued directly on the surface of the peri- one pole is identified, it is divided between ties at its superior cardium. This posterior dissection is carried as far down as possi- extent. Its medial edge is then followed down to where it meets the ble, primarily in a blunt fashion. Most of the time, the surgeon medial edge of the opposite superior pole, and this opposite pole holds one ring clamp containing a sponge dissector in each hand, can then be similarly traced upward into the neck, ligated, and while an assistant holds the upper poles. Occasionally, the surgeon divided. A very important part of the procedure is the placement holds the sutures attached to the upper poles in one hand while of 0 silk ligatures around an area containing strong tissue within employing the sponge dissector in the other hand. each superior pole.These ligatures are left long and clamped.The surgeon or an assistant places traction on them during the remain- Step 7: removal of specimen. When the posterior dissection has ing course of the dissection to manipulate and progressively mobi- been extended as far as possible toward the diaphragm, further lize the gland [see Figure 8]. mobilization of the thymus is typically accomplished by working the glandular tissue laterally, first off the pleura on one side, then Step 3: continuation of dissection downward into superior mediasti- off the sternum anteriorly, and finally off pleura on the opposite num. As traction is being placed on the upper poles, sharp and side. In this way, the entire gland is ultimately removed between blunt dissection, staying outside the well-defined capsule of the the phrenic nerves and down to the diaphragm. During this final gland, is extended downward into the superior mediastinum to mobilization, the surgeon periodically asks to have ventilation held the level of the innominate vein. The procedure becomes much temporarily so that the pleura can fall back and thus permit more difficult if the capsule is violated. improved visualization. Small feeding vessels from the mammary are doubly clipped and divided as they are encountered. Step 4: elevation of sternum. Finger dissection is performed in the Often, the final stages of blunt dissection may be facilitated by substernal plane, and the arm of a Cooper thymectomy retractor is placing a ring clamp on the body of the gland to allow slightly placed into the retromanubrial space to elevate the sternum. The more vigorous retraction than can be achieved by using the upper retracting arm is placed under upward tension as the inflatable bag poles alone. If any suspicious residual tissue is seen in the medi- beneath the shoulders is deflated. This step leaves most patients astinum at this point, it can be removed piecemeal; however, this actually hanging from the retractor, thereby opening up a sizable is an unusual occurrence. space that allows good visualization and ready passage of dissecting instruments into the anterior mediastinum. Army-Navy retractors Step 8: closure. After inspection of the surgical field for hemo- are placed in each of the two upper corners of the incision, and their stasis, the strap muscles and the platysma are closed over a red distal ends are tied to the siderails of the table with Penrose drains rubber catheter, to which suction may be applied. The catheter is to provide countertraction and to hold the skin incision open. subsequently removed, and the skin is closed. Step 5: dissection of venous tributaries to innominate vein. With the Troubleshooting In the course of preoperative evaluation superior poles gently pulled upward by an assistant (and at times before TCT, it is important to be sure that the patient is able to looped over the Cooper retractor), the inferior surface of the gland extend the neck to a reasonable degree.TCT is simplest in young is dissected until the innominate vein is encountered. The venous persons who are capable of good extension; it can be difficult or tributaries draining the thymus into the innominate vein are iso- impossible in persons with cervical spine disease that hinders lated sharply, ligated with fine silk sutures, and divided. extension.
  7. 7. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 7 During the procedure itself, it is important that the branches of Occasionally, a seroma develops at the site of the incision, but it the innominate vein be tied rather than clipped; the space anteri- almost always resolves either spontaneously or after a single per- or to the vein becomes the avenue through which dissecting instru- cutaneous drainage procedure in the office. ments are passed into and out of the mediastinum, and these instruments often rub against the vein fairly vigorously. When working laterally, one must take care not to injure the Procedures for Lesions of the Middle Mediastinum phrenic nerves, and one certainly should not use the electro- The majority of masses found in the middle mediastinum in cautery while working at the lateral extremes of the dissection. If adults are malignant, representing either lymphoma or lymph the pleural space is entered while one is working laterally, a red node metastases from primary lung carcinoma. Accordingly, the rubber catheter [see Operative Technique, Step 8, above] is advanc- procedures performed in this anatomic area primarily involve ed well into that pleural space, and suction in the form of several biopsy for staging or diagnosis rather than curative or palliative large positive pressure breaths is applied before the catheter is resection. On infrequent occasions, however, benign or primary removed. malignant lesions of the middle mediastinum occur for which If a thymoma is encountered during TCT, continuation via this resection is appropriate. In what follows, we briefly discuss resec- approach may be considered. In our view, most noninvasive tion of such lesions; for the most part, the principles are the same thymic lesions less than 3 cm in diameter can be safely and com- as those underlying resection of masses in the posterior medi- pletely resected via the transcervical approach. In addition, it gen- astinum [see Procedures for Lesions of the Posterior Mediastinum, erally is not difficult to resect a portion of the anterior pericardi- below]. um as well if a tumor or the thymus is adherent to it. However, Of particular surgical interest in the middle mediastinum are because the evidence currently available does not conclusively benign cysts, which may arise from the pleura, the pericardium, establish that TCT is equivalent to resection via sternotomy for the airways, or the esophagus. Bronchogenic cysts, which typical- thymoma, some surgeons prefer to convert to a sternotomy if a ly develop in proximity to the carina, are probably the middle suspicious mass is discovered during transcervical exploration. mediastinal cysts most commonly encountered in clinical practice, Certainly, if any difficulty is encountered that might lead to an with pericardial cysts running a close second. On rare occasions, incomplete thymectomy or incomplete removal of a thymoma, the ectopic remnants from cervical structures (e.g., the parathyroid incision should be extended. and thyroid glands) are encountered in this compartment.16 Approximately 90% of patients are able to go home on the same PREOPERATIVE EVALUATION day as their procedure. The most common cause for hospital admission is a pneumothorax that must be monitored or drained. CT generally provides an accurate preoperative diagnosis of a benign middle mediastinal cyst, as well as information regarding abutment of adjacent structures, the consistency of the mass, and potential invasiveness. MRI may be helpful if there is concern that a cyst might actually represent an aberrant vascular structure or an aneurysm, if the simple nature of the cyst is in doubt, or if clearer delineation of suspected invasion of surrounding structures is re- quired. Radionuclide scans (e.g., with technetium-99m or radio- active iodine) may be useful if the differential diagnosis includes a parathyroid or thyroid mass. Cystic structures adjacent to the air- ways and the esophagus are evaluated by means of bronchoscopy, esophagoscopy, barium esophagography, or some combination of these imaging modalities to rule out communication with the lumina. OPERATIVE PLANNING Middle mediastinal cysts that are symptomatic should be treat- ed surgically. However, simple cysts of the middle mediastinum that are asymptomatic and meet all radiographic criteria for benig- nity may be followed. This conservative approach is often more appropriate for asymptomatic middle mediastinal cysts than for asymptomatic posterior mediastinal cysts, in that complete cyst resection (at least, for bronchogenic cysts) tends to be more com- plex in the middle mediastinum than in the posterior mediasti- num, given the closer proximity to vital structures and the deeper placement within soft tissue. Complete resection of pericardial cysts, on the other hand, typically is easily accomplished by means of VATS; therefore, such cysts are probably best resected when dis- covered, even if they are asymptomatic. Although VATS resection of subcarinal bronchogenic cysts is feasible and has been described in published reports,17 it is our experience that in many Figure 8 Resection of anterior mediastinal mass: transcervical instances, this approach leaves behind more than a small portion approach. A Cooper thymectomy retractor is placed beneath the of the cyst wall. sternum, and retraction on the upper poles of the thymus is Thus, for a symptomatic subcarinal bronchogenic cyst (a not maintained with silk sutures. uncommon occurrence), one is left to choose between (1) thora-
  8. 8. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 8 cotomy for complete resection and (2) some other approach for incomplete resection. Because this area is easily accessible by means Table 2 Indications for Planned Thoracotomy of mediastinoscopy, and because we believe that mediastinoscopy Approach to Middle or Posterior Mediastinal Mass both is simpler and causes less morbidity than VATS, we prefer par- tial resection via mediastinoscopy as the initial approach to these Suggestion of malignancy on preoperative radiography lesions.18 If cysts treated in this manner recur with associated symp- Presence of inflammation or infection, blurring tissue planes toms, one can always perform thoracotomy for complete resection Large mass (> 5–6 cm) at that time, and little will have been lost in the meantime. Esophageal duplication cyst believed to communicate with esophageal lumen on the basis of preoperative CT, barium esophagography, or esophagoscopy MEDIASTINOSCOPIC PARTIAL RESECTION OF SUBCARINAL Esophageal lesions without evidence of overlying normal esophageal BRONCHOGENIC CYST mucosa on preoperative esophagoscopy or endoscopic ultrasonography Operative Technique Previous ipsilateral thoracotomy with adhesions Tumor located at apex of the chest, which may necessitate Step 1: mediastinoscopy and pretracheal dissection A thoracosternotomy standard cervical mediastinoscopy is performed, with dissection in the pretracheal plane down to the level of the carina. generally,VATS results in less postoperative pain and quicker func- Step 2: freeing of cyst from surrounding tissues With tional recovery.19,20 Some surgeons argue that a VATS approach the cyst wall kept intact, as much of the wall as can safely be may be more likely to leave a patient with microscopic residual dis- exposed is visualized by bluntly dissecting it away from the under- ease. In our experience and that of others, however, recurrences of surface of the carina and the mainstem bronchi. Next, the mass is these lesions are very rare after VATS excision.21,22 Given the low dissected away from the soft tissues anterior and posterior to it; recurrence rate and the fact that these masses are almost always obviously, this must be done with caution, given that the right benign, we believe that the risk-benefit ratio is better with VATS in main pulmonary artery and the esophagus are located nearby (an- most cases. teriorly and posteriorly, respectively). There are, however, several circumstances in which thoracoto- my is indicated from the outset [see Table 2]. A suggestion of malig- Step 3: aspiration of cyst contents and excision of exposed nancy (in particular, invasion of surrounding structures) on pre- cyst wall The contents of the cyst are aspirated for cytologic operative radiography mandates exploration and resection by tho- and microbiologic examination, and the exposed portion of cyst racotomy; in this situation, the potential consequences of positive wall is excised. Typically, approximately 50% of the cyst wall can margins justify the more aggressive approach. The presence of be removed in this fashion. Some of the remaining cyst wall may active infection within a cyst is a relative indication for thoracoto- be cauterized; this too must be done with caution, given the prox- my, in that it can cause disruption of normal tissue planes and imity of the adjacent vital structures. thereby render VATS dissection more hazardous. Masses larger than approximately 6 cm also call for an open approach: such lesions are typically more difficult to mobilize safely from underly- Procedures for Lesions of the Posterior Mediastinum ing structures than smaller lesions are, they are more likely to be The majority of posterior mediastinal masses occurring in adults malignant, and their removal between the ribs is likely to necessi- are benign. These lesions may be usefully classified according to tate rib spreading, which may negate some of the benefit of true their radiologic appearance—that is, as either cystic or solid. Cys- VATS. tic masses in this region typically are bronchogenic cysts or esoph- When a cyst is arising from or abutting the esophagus, the pos- ageal duplication cysts, whereas solid masses most frequently are sibility of a communication between the cyst and the esophageal benign neurogenic tumors (e.g., schwannomas, neurofibromas, or ganglioneuromas). Esophageal leiomyomas (benign intramuscular tumors within the esophageal wall) are often grouped with these posterior mediastinal lesions and are managed in a similar fashion. In many cases, posterior mediastinal masses come to light as asymptomatic radiographic abnormalities; however, they may also be associated with signs of infection (in the case of infected cysts), dysphagia, chest pain, or respiratory complaints. At pres- ent, because of the growing availability of less morbid, minimally invasive approaches to posterior mediastinal masses, most authors recommend resection even when the lesion is asymptomatic. Al- though this recommendation remains somewhat controversial, we agree with it. OPERATIVE PLANNING VATS versus Thoracotomy Resection of posterior mediastinal masses may be accomplished by means of either VATS or thoracotomy. The procedure is essen- tially the same with either approach, and the goal is complete resec- Figure 9 Resection of neurogenic tumor of posterior medi- tion. With some exceptions, VATS [see 4:10 Video-Assisted Thoracic astinum. Intraoperative photo shows a solid neurogenic tumor of Surgery] is considered preferable to thoracotomy in this setting; the costovertebral sulcus.
  9. 9. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 9 sought before operation from all patients being treated for posteri- or mediastinal lesions, even when VATS is the intended approach. VATS RESECTION OF NEUROGENIC TUMOR OF POSTERIOR MEDIASTINUM Operative Technique Alternative Upper Resection of a solid neurogenic tumor of the posterior medi- Working Ports astinum that does not invade the neural foramen [see Figure 9] pro- ceeds as follows. Step 1: intubation and endoscopy The patient is intubated Tumor with a double-lumen endotracheal tube to allow single-lung venti- lation. Preoperative bronchoscopy (for cystic lesions) or esoph- agoscopy (for lesions abutting the esophagus) is performed as indicated (see above). Camera Port Step 2: patient positioning and placement of ports The patient is placed in the lateral thoracotomy position and stabilized Lower with bean bags so that the operating table can safely be tilted as Working Port much as 45° to either side. With this degree of tilt, the lung tends to fall away from the field of vision; thus, there usually is no need Figure 10 Resection of neurogenic tumor of posterior medi- to place an additional port for a lung retractor. astinum. Shown is typical port placement for VATS resection of a The port for the scope is placed through an incision in the posterior mediastinal mass. midaxillary line at the level of the mass; if it is placed much more anteriorly than the midaxillary line, the surgeon’s view of posteri- or lesions may be obscured by the lung.The two working ports are lumen should be investigated preoperatively. Such a communica- placed through separate incisions in the posterior axillary line, tion may be suggested on CT scans by the presence of an air-fluid made as far cephalad and caudad as possible. Sometimes, place- level. To rule out this phenomenon, we perform barium esopha- ment of an alternative upper working port posterior to the scapu- gography during the preoperative workup, followed by intraopera- la is advantageous [see Figure 10]. The main working instruments tive esophagoscopy at the commencement of the operation. If a are an endoscopic scissors-cautery, a ring clamp, an endoscopic pea- communication is identified or cannot be ruled out, thoracotomy nut dissector, a Maryland dissector, a long right-angle clamp, and is performed. After excision of an esophageal duplication cyst with an endoscopic clip applier. a communication, reapproximation of the esophageal mucosa is a paramount consideration; in our view, this is best done through an open approach. In cases of suspected leiomyoma of the esophagus, preoperative investigation should be done to confirm the presence of intact overlying mucosa, which is virtually pathognomonic of this dis- ease. Esophagoscopy is done to assess the mucosa; if the mucosa is intact, the possibility of malignancy is essentially ruled out. Simultaneously, endoscopic ultrasonography may be performed to establish the depth to which the esophageal wall is involved. With a preoperative diagnosis of probable leiomyoma, VATS is the approach of choice in our practice. So-called dumbbell neurogenic tumors (tumors that invade the neural foramen) are special cases. Any solid mass in the costover- tebral sulcus should be evaluated by means of MRI to determine whether it is invading the neural foramen if the absence of invasion was not clearly established by CT. Although invasion of the neural foramen by tumor is not in itself an indication for thoracotomy, it does necessitate a combined anterior-posterior approach with neu- rosurgical involvement for the intraspinal portion of the procedure. Several versions of such an approach have been described.23-25 We prefer to perform the posterior neurosurgical resection of the intra- spinal component (laminectomy and intervertebral foraminotomy) first, then to reposition the patient and carry out the remainder of the procedure (via VATS or thoracotomy).26 Although VATS is often an excellent approach to posterior mediastinal lesions, it must be emphasized that one should never Figure 11 Resection of neurogenic tumor of posterior medi- hesitate to convert a VATS procedure to a thoracotomy if required. astinum. Shown is circumferential incision of the pleura around a Accordingly, informed consent to undergo thoracotomy should be neurogenic mass.
  10. 10. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 10 brospinal fluid leak, which most often becomes evident only post- operatively (in the form of persistent clear chest tube output).The diagnosis of CSF leakage can be confirmed by measuring the β2- transferrin level in the fluid. If CSF leakage is confirmed, reopera- tion with a neurosurgeon is mandatory; the leak is repaired and buttressed with vascularized tissue. After resection of a tumor at the costoverterbral sulcus, regular neurologic examinations of the lower extremities are indicated. Tamponade with hemostatic agents should never be employed for bleeding at the neural foramen: doing so can result in an intra- spinal hematoma with subsequent cord compression. Careful use of the electrocautery at the bony margins of the foramen or watch- ful waiting is preferable. If hemostasis cannot be achieved with these measures, a neurosurgical consultation should be obtained. In the event of oozing from the vicinity of a foramen that is not eas- ily controlled, there should be no hesitation in converting a VATS procedure to an open procedure. In a minority of patients, clipping and division of an intercostal Figure 12 Resection of neurogenic tumor of posterior medi- nerve results in intercostal neuralgia after the procedure; the pos- astinum. The final remaining intercostal stalk is divided. sibility that this may occur must be discussed with the patient pre- operatively. Many patients who undergo division of a lower tho- racic intercostal nerve that supplies an upper abdominal derma- Step 3: incision of pleura The parietal pleura is incised tome notice postoperative bulging of the ipsilateral abdomen in the around the mass, with a margin of approximately 2 cm circumfer- area supplied by that nerve. entially. The pleura is tented up with the aid of the right-angle clamp or the Maryland dissector to separate it from the underly- RESECTION OF BENIGN CYST OF POSTERIOR MEDIASTINUM ing structures [see Figure 11]. This separation allows the use of the Resection of a benign cystic mass of the posterior mediastinum electrocautery, which provides hemostasis while protecting the closely resembles resection of a neurogenic tumor [see Resection of underlying esophagus, vagus and intercostal nerves, and azygos Neurogenic Tumor of Posterior Mediastinum, above]; the differ- vein. This dissection and all subsequent work are facilitated by ences are relatively minor [see Troubleshooting, below]. placing gentle traction on the mass with a sponge stick or, for smaller masses, by grasping the entire mass within a ring clamp. Troubleshooting In the initial stages of dissection of a benign cyst of the posteri- Step 4: dissection of soft tissue attachments Once the or mediastinum, care should be taken not to rupture the cyst; ini- pleura has been incised circumferentially, the soft tissue attach- tial mobilization from surrounding structures is easier when the ments are further dissected bluntly with the endoscopic peanut cyst wall is under tension [see Figure 13]. If the area of the cyst wall dissector. Attachments that are relatively thick or vascular are best that directly abuts the mediastinum is found to be too adherent to controlled by double-clipping and division. If the tumor originates underlying structures to be removed safely, we intentionally rup- from an intercostal nerve, gentle dissection is done beneath the ture the cyst, then remove as much of the cyst wall as possible. As tumor to identify the intercostal bundle that is the source of the much as 35% of the cyst wall may be left in place. In such cases, lesion. Step 5: division of source intercostal bundle The source intercostal bundle lateral to the tumor is mobilized, doubly clipped, and divided. Once this has been accomplished, blunt dissection is performed until the nerve root emerging from the neural foramen and the associated intercostal vessels are the last remaining attach- ments. If the tumor originates from the sympathetic chain, the chain is clipped above and below the tumor, and the intercostal bundle is spared if possible. Step 6: removal of specimen The remaining stalk is doubly clipped and divided [see Figure 12], and the mass is removed in an endoscopic bagging device. Step 7: drainage A 24 French chest tube is positioned pos- teriorly at the apex. Troubleshooting Care must be taken to ensure that only very gentle traction is exerted on a mass adjacent to the neural foramen. Overzealous Figure 13 Resection of benign cyst of posterior mediastinum. traction can cause tearing of the nerve root proximal to the Intraoperative photo shows a fluid-filled posterior mediastinal extraspinal extent of the dura, and this tearing can lead to a cere- cyst. The tenseness of the cyst wall facilitates initial dissection.
  11. 11. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 11 a b c d e f Figure 14 Resection of esophageal leiomyoma. (a) Shown is an esophageal leiomyoma beneath the azygos vein. (b) The mediastinal pleura overlying the leiomyoma is incised. (c) The azygos vein is divided with an endoscopic stapler. (d) The muscle fibers overlying the mass are divided. (e) Gentle traction is applied to facilitate blunt dissection. (f) Shown is a completely resected horseshoe-shaped esophageal leiomyoma. we ablate the residual intact cyst wall with the electrocautery to cedure [see Figure 14e]. Having an assistant place the endoscope destroy any potential secretory tissue. If more than approximately within the esophageal lumen to distend and illuminate the 35% of the cyst must be left in place, conversion to thoracotomy mucosa also may be helpful at this stage. Once the mass has should be considered. been completely resected, it is sent for pathologic examination [see Figure 14f]. RESECTION OF ESOPHAGEAL LEIOMYOMA 5. The esophagus is distended by insufflating air from above while Operative Technique the distal esophagus is occluded with a sponge stick. The air- filled esophagus is then submerged in saline, and the area of the In addition to the steps described for resection of a neurogenic resection is examined for air leakage. mass, there are several special maneuvers that facilitate resection of esophageal intramural masses, such as leiomyomata [see Figure Troubleshooting 14a] and duplication cysts. Some surgeons routinely close the muscular defect in the esoph- 1. The pleura is incised longitudinally with the electrocautery agus after resection so as to reduce the risk that an esophageal after it is tented up away from the esophagus, the vagus nerve, diverticulum will develop. Such closure may be accomplished by and the azygos vein with a right-angle clamp or a Maryland dis- means of thoracoscopic suturing. Often, though, the muscle layer sector [see Figure 14b]. is attenuated to the point where useful reapproximation is nearly 2. In some cases, exposure is facilitated by dividing the azygos vein impossible. For this reason, as well as because we believe that a with an endoscopic stapler [see Figure 14c]. diverticulum is unlikely to develop in the absence of a distal func- 3. The longitudinal esophageal muscle fibers that overlie the mass tional obstruction, we do not routinely close the muscular defect. are separated bluntly or with the electrocautery.These fibers are Frequently, duplication cysts are more adherent to the under- often markedly attenuated as a result of the expansion of the lying esophageal mucosa than leiomyomata are, and transillumi- mass [see Figure 14d]. nation of the esophageal wall helps define the plane at which blunt 4. Blunt dissection with an endoscopic peanut dissector allows dissection should be performed.Where the cyst wall becomes dif- careful, progressive mobilization of the mass, first from the ficult to separate from the mucosa, a small amount of the wall may muscle layer and then from the underlying mucosa. Gentle be left in place if, in the surgeon’s judgment, attempting to remove traction on the mass facilitates exposure at this point in the pro- all of it might lead to a breach in the mucosa.
  12. 12. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 4 THORAX 11 MEDIASTINAL PROCEDURES — 12 References 1. Hoerbelt R, Keunecke L, Grimm H: The value of Ann Thorac Surg 79:450, 2005 20. Nagahiro I, Andou A, Aoe M, et al: Pulmonary a noninvasive diagnostic approach to mediastinal 11. Blalock A, Masoj MF, Riven SS: Myasthenia gravis function, postoperative pain, and serum cytokine masses. Ann Thorac Surg 75:1086, 2003 and tumors of the thymic region. Ann Surg 110: level after lobectomy: a comparison of VATS and 2. Koduri P: The diagnostic approach to mediastinal 544, 1939 conventional procedure. Ann Thorac Surg 72:362, masses. Ann Thorac Surg 78:1888, 2004 2001 12. Shrager JB, Deeb ME, Mick R, et al: Transcervical 3. Vernino S, Lennon VA: Autoantibody profiles and thymectomy for myasthenia gravis achieves results 21. Martinod E, Pons F, Azorin J, et al: Thoracoscopic neurological correlations of thymoma. Clin Cancer comparable to thymectomy by sternotomy. Ann excision of mediastinal bronchogenic cysts: results Res 10:7270, 2004 Thorac Surg 74:320, 2002 in 20 cases. Ann Thorac Surg 69:1525, 2000 4. Drevelegas A, Palladas P, Scordalaki A: Mediastinal 22. Zambudio AR, Lanzas JT, Calvo MJ, et al: Non- 13. Cooper JD, Al-Jilaihawa AN, Pearson FG, et al: An germ cell tumors: a radio-pathological review. Eur neoplastic mediastinal cysts. Eur J Cardiothorac improved technique to facilitate transcervical Radiol 11:1925, 2001 Surg 22:712, 2002 thymectomy for myasthenia gravis. Ann Thorac 5. Schneider DT, Calaminus G, Reinhard H, et al: Surg 45:242, 1988 23. Shadmehr MB, Gaissert HA, Wain JC, et al: The Primary germ cell tumors in children and adoles- surgical approach to “dumbbell tumors” of the 14. Bril V, Kojic J, Ilse WK, et al: Long-term clinical cents: results of the German cooperative protocols mediastinum. Ann Thorac Surg 76:1650, 2003 outcome after transcervical thymectomy for myas- MEKEI 83/86, 89 and 96. J Clin Oncol 18:832, thenia gravis. Ann Thorac Surg 65:1520, 1998 24. Osada H, Aoki H,Yokote K, et al: Dumbbell neu- 2000 rogenic tumor of the mediastinum: a report of three 15. Calhoun RF, Ritter JH, Guthrie TJ, et al: Results of cases undergoing single-staged complete removal 6. Wood DE: Mediastinal germ cell tumors. Semin transcervical thymectomy for myasthenia gravis in without thoracotomy. Jpn J Surg 21:224, 1991 Thorac Cardiovasc Surg 12:278, 2000 100 consecutive patients. Ann Surg 230:555, 1999 7. Watanabe M, Takagi K, Aoki T: A comparison of 25. Rzyman W, Skokowski J,Wilimski R, et al: One step biopsy through a parasternal anterior mediastinot- 16. Nwariaku F, Snyder WH, Burkey SH, et al: Infra- removal of dumb-bell tumors by postero-lateral omy under local anesthesia and percutaneous nee- manubrial parathyroid glands in patients with pri- thoracotomy and extended foraminectomy. Eur J dle biopsy for malignant anterior mediastinal mary hyperparathyroidism: alternatives to ster- Cardiothorac Surg 25:509, 2004 tumors. Surg Today 28:1022, 1998 notomy. World J Surg, March 22, 2005 [Epub ahead of print] 26. Vallieres E, Findlay JM, Fraser RE: Combined 8. Powers CN, Silverman JF, Geisinger KR, et al: microneurosurgical and thorascopic removal of Fine-needle aspiration biopsy of the anterior medi- 17. Demmy TL, Krasna MJ, Detterbeck FC, et al: Mul- neurogenic dumbbell tumors. Ann Thorac Surg 59: astinum: a multi-institutional analysis. Am J Clin ticenter VATS experience with mediastinal tumors. 469, 1995 Pathol 105:168, 1996 Ann Thorac Surg 66:187, 1998 9. Deeb ME, Brinster CJ, Kucharzuk J, et al: Expand- 18. Smythe WR, Bavaria JE, Kaiser LR: Mediastino- ed indication for transcervical thymectomy in the scopic subtotal removal of mediastinal cysts. Chest Acknowledgments management of anterior mediastinal masses. Ann 114:1794, 1998 Thorac Surg 72:208, 2001 Figure 1b Photo courtesy of Wallace T. Miller, Sr., 19. Santambrogio L, Nosotti M, Bellaviti N, et al: M.D., University of Pennsylvania School of Medicine. 10. Savitt MA, Gao G, Furnary AP, et al: Application Videothoracoscopy versus thoracotomy for the diagnosis of the intermediate solitary pulmonary Figures 2, 7, and 8 Alice Y. Chen. of robotic-assisted techniques to the surgical evalu- ation and treatment of the anterior mediastinum. nodule. Ann Thorac Surg 59:868, 1995 Figure 10 Tom Moore.