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Posterior Mediastinal Lesions : A Short Review

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Posterior mediastinal lesions

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Posterior Mediastinal Lesions : A Short Review

  1. 1. Posterior Mediastinal Lesions Alireza Kashani
  2. 2. Mediastinal Compartments  Posterior Mediastinum:  Also called paravertebral compartment  Defined by :  Posterior Pericardium  Anterior Spinal Ligament  Superiorly: T4 vertebral body  Inferiorly: Diaphragm  Contains:  Oesophagus, Descending Aorta, Sympathetic Chain, Vagus Nerves, Thoracic Duct, Azygos and Hemiazygos veins, and Lymph Nodes
  3. 3. Epidemiology  Adults:  65% anterosuperior  10% middle  25% posterior compartments  Children:  25% anterosuperior  10% middle  65% in posterior compartments  Generally the incidence of posterior mediastinal lesions is higher in children.  50% are asymptomatic and are diagnosed incidentally  The absence of symptoms is generally is a clue to a benign lesion  Symptomatic lesions:  Children: 60%-80%  Adults: 50%-60%
  4. 4. Diagnosis  CT Scan is the diagnostic modality of choice and is superior to even MRI in majority of the cases  MRI rarely indicated  Thoracic US is not helpful in posterior mediastinal lesions  Biopsy: is not necessary in majority of the cases and likelihood of a positive result parallels the presence of symptoms  If needed:  CT-guided  Thoracoscopic  Limited posterolateral thoracotomy
  5. 5. Neurogenic Tumours  Young adults and children  They are the most common malignant neoplasm in children but they are less common than anterior mediastinal malignancies in adults.  Lymphomas and Thymomas are more common in adults  Malignancy rate:  Children: 50%  Adults: 10%  They originate from embryonic neural crest cells around the spinal ganglia and from either sympathetic or parasympathetic components
  6. 6. Neurogenic Tumours  Source:  Intercostal nerve:  Neurofibroma : benign  Of patients with nerve sheath tumours 25%-40% have multiple neurofibromatosis (von Recklingausen’s disease) and the incidence of malignancy is more common in these patient  Neurilemoma (Schwannoma) :  Mostly benign but malignant schwannomas are rare  The most common neurogenic tumor  Neurogenic Sarcoma (rare)  Sympathetic Ganglia: can also have pheochromocytoma  Ganglioneuroma  Ganglioneuroblastoma  Neuroblastoma  Other: phrenic nerves, Vagus nerves
  7. 7. Neurogenic Tumours  Those with benign lesions are generally asymptomatic  Malignant tumors might present with symptoms such as:  Spinal cord compression  Cough  Dyspnea  Chest wall pain  Hoarseness  Rarely Horner’s syndrome  Rarely pheochromocytoma:  Neuroblastoma or ganglioneuroma  In all symptomatic patients, esp. those with significant hypertension it is necessary to check for 24 h urine HVA (homovanillic acid) and VMA (vanillylmandelic acid)  If elevated then prior to operation to avoid adrenergic crisis:  α-adrenergic blockers  beta-blockers
  8. 8. Neurogenic Tumours  Intercostal nerves:  Neurofibroma  Poorly encapsulated  Random arrangement of spindle-shaped cells  Neurilemomas  The most common neurogenic tumor  Well-encapsulated  Firm, gray-tan  Two morphologic types:  Antoni’s type A:  Organized architecture with a cellular palisading pattern of growth  Antoni’s type B:  Loose reticular pattern  Both of the above can happen as parts of neurofibromatosis type 1 (von Recklinghausen’s disease) and if left untreated can degenerate to neurosarcoma
  9. 9. Neurofibroma
  10. 10. Neurilemmoma – Mixed A and B
  11. 11. Neurilemmoma – Antoni A
  12. 12. Neurilemmoma – Antoni B
  13. 13. Sympathetic Source
  14. 14. Sympathetic Source  Neuroblastic Tumors:  Arising from primitive sympathetic ganglia  Comprise:  Neuroblastoma  Ganglioneuroblastoma  Ganglioneuroma  These differ in their degree of cellular and extracellular maturation  Immature tumors:  Tend to be aggressive  Occur in younger patients (median age < 2)  Mature tumors:  Older children (median age 7)  More benign  Anywhere sympathetic nervous tissue exists:  Neck  Posterior Mediastinum  Adrenal Gland  Retroperitoneum  Pelvis
  15. 15. Sympathetic Source  Ganglioneuroma:  The most common neurogenic tumor occurring in children  Benign  Composed of gangliocytes and mature stroma  Early age  Located in the paravertebral region  Ganglioneuroblastoma:  Composed of mature gangliocytes and immature neuroblasts  Intermediate malignant potential
  16. 16. Ganglioneuroma
  17. 17. Ganglioneuroma
  18. 18. Sympathetic Source  Neuroblastoma:  Children < 4 y  Small, round immature cells organized in rosette pattern  Highly invasive  Metastasized by the time the diagnosis is made:  Regional lymph nodes, bone, brain, liver, lung  Some may have benign course  Symptoms:  Cough, dysphagia, chest pain, and occasionally paraplegia  Paraneoplastic:  Profuse watery diarrhea due to VIP  Opsoclonus-Polymyoclonus syndrome  Pheochromocytoma-like syndrome  Prognosis:  Influenced by: DNA content, tumor proto-oncogenes, and catecholamine synthesis  The above aid in categorizing patients with neuroblastoma into low, intermediate, and high-risk  Rx: Resection +/- Chemotherapy
  19. 19. Neuroblastoma
  20. 20. Neuroblastoma
  21. 21. Investigations  CT:  Can help to identify the tumor and extent of involvement  Those from peripheral nerves:  Well-defined, round or oval masses  Noncalcified  Neurilemoma:  Variable enhancement: homogenous or heterogenous  On enhanced CT: variable attenuation  Neurofibroma:  Usually homogenous  Low-attenuation  On enhanced CT: homogenous enhancement or with early central blush  Malignant nerve sheath tumors show variable attenuation
  22. 22. Investigations  CT:  Sympathetic Chain Tumors:  Expand along the spinal axis  No calcification or bone changes  Ganglioneuroma:  Oblong homogenous low-attenuation lesions on both enhanced and unenhanced CT  Neuroblastoma:  Aggressive soft tissue lesions with calcification  Ganglioneuroblastoma:  Mixed features of above  Paragangliomas:  Appear in aortopulmonary window  High contrast enhancement
  23. 23. Investigations  MRI: for dumbbell tumors  FNA  Tumor Markers: S-100
  24. 24. Dumbbell Tumors  Tumors of the posterior mediastinum that extend into the spinal canal via the intervertebral foramen  It is necessary to identify these tumors to have a better planning, as inaccurate diagnosis would lead to intra-spinal hemorrhage and cord compression  MRI can identify these  Smoothly rounded, homogenous density abutting the vertebral column  Rarely present with cord compression symptoms  They comprise 10% of patients with neurogenic tumors  Only 1-2% are malignant
  25. 25. Management  Standard of Care:  Surgical resection via thoracotomy or thoracoscopy  Most of the neurogenic tumors can be resected via thoracoscopy; however, malignant transformation, local invasion, and tumors larger than 5 cm increase the likelihood of conversion to thoracotomy  In most cases the tumor can easily be mobilized via thoracoscopy but any difficulty necessitates the conversion to thoracotomy  Resection of the nerve root is necessary in most of the cases  A widened intervertebral foramen might be indicative of invasion of vertebral canal (dumbbell tumor) and in these cases it is necessary to involve a neurosurgeon to assist in full resection of the tumor via a laminectomy in one stage procedure  Neuroblastoma:  Spontaneous regression has been reported  Stage:  I (noninvasive): Surgical resection alone  II (locally invasive on same side of midline): Surgery + RTx  III (invasive across the midline): Debulking + RTx + ChemoTx + Second-look operation  Children < 1 : good prognosis, prognosis has inverse correlation with age
  26. 26. Oesophageal Masses  These include:  Neoplasm  Cysts  Diverticula  Hiatal Hernia  Mega-oesophagus  Oesophageal Varices
  27. 27. Cysts  Rare, benign, congenital  20% of all mediastinal lesions  Include:  Bronchogenic  Hydatid  Enteric  Intramural Oesophageal  Neuroenteric Cysts  CT is the most effective modality of diagnosis
  28. 28. Bronchogenic  60% of all mediastinal cysts  Location:  Lung parenchyma  Mediastinum  Histology:  Ciliated columnar epithelium  Cyst wall: cartilage, mucus glands, smooth muscle  Rarely communicate with the tracheobronchial tree  Symptoms:  Occasional compression on the adjacent structures  Recurrent infection  Pain, Cough, Hemoptysis  Rx:  If incidental finding in an otherwise asymptomatic patient: observation is accepted  If symptomatic esp. if pain, cough, or hemoptysis the resection is strongly advised.
  29. 29. Bronchogenic
  30. 30. Bronchogenic
  31. 31. Bronchogenic  Dysphagia: as a result of compression effect on the oesophagus  Presence of air-fluid level: suggests the possibility of communication with the tracheo-bronchial tree and increased chance of recurrent infections; hence, the possible need for resection  If it becomes infected, it is very likely that eradication is unsuccessful and it needs to be resected  Symptoms tend to develop with time and hence the resection is advised in a healthy state before becoming symptomatic.  They can be resected via thoracoscopy or if in superior mediastinum via mediastinoscope.
  32. 32. Bronchogenic
  33. 33. Bronchogenic
  34. 34. Gastroenteric Cysts  Gastroenteric or duplication cysts: peri-oesophageal lesions that arise from posterior division of the primitive foregut.  Features:  Posterior or middle mediastinal mass  Within or adjacent to the oesophageal wall  Communication with UGIT is uncommon  Histology:  Nonkeratinizing squamous, ciliated columnar, gastric, or small intestinal epithelium  Epithelium is not a good differentiating feature from bronchogenic cysts:  Presence of two muscular layers in oesophageal cysts  Cartilage and bronchial glands in bronchogenic cysts  Usually asymptomatic, but symptoms:  Resp: Cough, SOB, Recurrent Pulmonary Infections, Chest Pain  If gastric mucosa: perforation into the oesophagus can cause haematemesis, or erosion into the adjacent lung can cause an abscess  Dx: EUS, Chest CT, Technetium Tc 99m (to identify gastric mucosa)  Rx:  Resection: symptomatic, unclear cysts – whether cystic or solid  Observation: clearly cystic lesions, otherwise asymptomatic
  35. 35. Gastroenteric Cysts
  36. 36. Gastroenteric Cysts
  37. 37. Neuroenteric Cysts  5-10% of foregut lesions  Infants younger than 1  Connection to the meninges usually through a stalk  Associated with the congenital defects of the spine  Endodermal and ectodermal or neurogenic elements  Failure of separation of the notochord from the primitive gut  CT evidence of mediastinal lesion with either of : Scoliosis, Hemivertebrae, Spina Bifida should prompt the possible Dx of neuroenteric cysts.
  38. 38. Other  Primary or metastatic lesions of thoracic spine  Lymphomas : esp. Hodgekins  Infections such as TB  Post-traumatic haematoma  Descending thoracic aneurysm  Extramedullary hematopoiesis  Castleman’s Disease  Angiomyolipoma  Extralobar Pulmonary Sequestration  Neuroendocrine Carcinoma  Mediastinal Ependymoma  Cellular Hemangiomas  Melanotic Paraganglioma  Pancreatic Pseudocyst Mediastinal Extension
  39. 39. Castleman’s Disease  Giant lymph node hyperplasia  Vascular tumors surrounded by large LAP  Types :  Localized: Hyaline Vascular, Plasma Cell  Generalized or Multicenteric  Hyaline Vascular: 90% of lesions  Incidental finding in otherwise asymptomatic  Spinal cord compression has also been reported  Rx: Surgical excision, RTx is ineffective  Plasma Cell:  More symptomatic: fever, fatigue, weight loss, hemolytic anemia, high ESR and hyper-γ- globulinemia as the result of the over production of IL-6  Resection is Rx of choice  Generalized:  Histologic features of both of the localized forms  Older patients  Symptoms:  Severe systemic symptoms  Generalized LAP  Hepatosplenomegaly  Mortality : 50% with median survival of 27 months and Progression to lymphoma
  40. 40. Castleman’s Disease - Hyaline
  41. 41. Castleman’s Disease - Plasma

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