Desmoid Tumor One of the most common benign soft tissue tumors is the extra-abdominal desmoid tumor, sometimes referred to as an aggressivefibromatosis or simple desmoid tumor. As compared to the multitudeof different clinical types of infantile fibromatosis, the desmoidtumor occurs in older children or young adults up through the ageof 40 years. The abdominal desmoid tumor is usually seen in youngadult females following pregnancy, whereas the extra-abdominaldesmoid tumor is found more commonly in men, usually in theproximal parts of the body such as the shoulder, buttock and posteriorthigh area. Other areas include the popliteal space, the arm andforearm. They are usually solitary lesions, however multi-centricinvolvement can occur. In the case of “Gardner’s syndrome” thedesmoid tumor can be associated with polyposis of the large boweland cranial-facial osteomas. Desmoid tumors take their origin frommuscle fascial planes and tend to be extensively infiltrative into thesurrounding tissue with poorly defined margins that make surgical
resection difficult. They can also occur in tendon sheaths, jointcapsules, and even inside bone. Clinically, the desmoid tumor hasthe appearance of a low grade fibrosarcoma but tends to be moreinvasive in character and can frequently engulf adjacent neuro-vascular structures. Even though the desmoid tumor has a histo-logical appearance similar to a low grade fibrosarcoma, it willnever metastasize to distant parts but can be multifocal in itspresentation in the extremity. Clinically, the desmoid tumor isvery firm to palpation. It frequently causes symptoms of pain andis tender on deep palpation. Microscopically the tumor is heavilycollagenized but with a very low mitotic index, with an appearancesimilar to plantar fibromatosis. The desmoid tumor does not calcify but is radiodense on ordinaryradiographs and can be easily identified on a soft tissue window CTscan. The MRI is the best imaging study for this tumor and will below signal on the T-1 weighted image but only intermediate highsignal on the T-2 because of the low water content in this tumor
which helps separate it from malignant MFH and fibrosarcoma.The desmoid tumor is related to physical activity compared tohigher grade spindle cell tumors that are more spontaneous in origin. Treatment consists of a wide surgical resection, if possible, butbecause of the high recurrence rate (about 50%), most clinicianswill advise post operative radiation therapy to the extent of 5000centigray to the surgical site starting two weeks after surgery. Thisreduces the chance of local recurrence to 10-15%. In rare situationswhere the patient has multiple recurrences locally following RT,amputation may be indicated. Even with amputation, recurrenceswill be seen at the amputation site. In patients over 40 years of ageit is not unusual to see a spontaneous involution of desmoid tumorsrequiring no treatment whatsoever. Estrogen may play a role in thedevelopment of desmoid tumors and this accounts for the use oftamoxifen with some reported clinical benefit. Other adjuvanttherapies include nonsteroidal anti-inflammatory agents and eventhe use of mild chemotherapeutic agents.
CLASSIC Case #250.1 Axial T-1 MRI 50 year male with desmoid tumor thigh
Elastofibroma The elastofibroma is seen almost exclusively in people past theage of 55 years. It is more common in women than men, and themajority of cases are seen in those involved in heavy manual laboror unusual sports requiring extensive use of the upper extremities.It almost always occurs between the scapula and the chest wallinferiorly and is bilateral in about 10% of cases. It is usually locatedin the lower subscapular area, deep to the rhomboid and latissimusdorsi muscles where it is firmly attached to the chest wall in the areaof the seventh and eighth ribs posteriorly. Grossly, the tumor has anappearance similar to a desmoid tumor and microscopically there isan intertwining of swollen eosinophillic collagen fibers and elasticfibers in an equal proportion. The elastic fibers have a degenerated,beaded appearance or are fragmented into small globules or dropletsthat are easily seen with the Verhoeff stain that is specific for elastinfiber. The cross section shows a characteristic serrated edge. The
elastofibroma is considered a reactive pseudotumor with an excellentprognosis. It is treated by a marginal surgical resection with anextremely low recurrence rate and in some cases can be treated byradiation therapy alone without surgery.
CLASSIC Case #255 Axial T-1 MRI 50 female with subscapular elastofibroma
Nodular Fascitis Nodular fascitis is a very common, self-limiting, reactive processrather than a true neoplasm occurring in young adults. Typically itarises spontaneously and rapidly in the subcutaneous portion of thelower aspect of the forearm and is associated with inflammatorypain, swelling and local tenderness. Histologically, nodular fascitiscan take on the appearance of a spindle cell sarcoma. The lesiongrows quite rapidly over a period of several weeks, is usuallysolitary, and usually occurs in the upper extremity. It is usually lessthan 3 cm in diameter, has a grayish-white appearance and can havemyxoid changes. Histologically, the lesion is a fibroblastic pseudo-tumor similar to granulation tissue with a fair number of mitoticfigures but no atypical mitoses will be seen. The fibroblasts areinfiltrated by lymphocytes. Treatment consists of local surgicalexcision with a rare recurrence rate of less than 2%. No adjuvanttherapy is indicated.
CLASSIC Case #256 25 year female with nodular fascitis forearm
Plantar Fibroma The plantar fibroma is a fairly common clinical entity similar toto the palmar fibroma. It arises from the plantar fascia and is usuallylocated on the medial portion of the arch of the foot. As opposed topalmar fibromatosis that is typically seen in older patients, the plantarfibroma is more common in young adults or even in children. Insome cases, there is a familial background (this is particularly truein Scandinavians), with a greater incidence in males. The plantarfibroma is frequently asymptomatic in which case surgical treatmentis not indicated. However, if pain results, especially if pressure on anadjacent central nerve causes symptoms, a simple surgical resectioncan be performed. Both the palmar and plantar fibromas have acharacteristic fibrotic histological appearance that is quite cellularin areas and can be misdiagnosed as a malignant sarcoma. Somepatients will have fibromas in their hands and feet simultaneouslyand can also have penile fibromas. A contracture of the finger istypical in palmar fibromas whereas toe contractures are not seen inplantar fibromatosis.
CLASSIC Case #257 32 year female with plantar fibroma
Malignant Fibrous Histiocytoma The malignant fibrous histiocytoma (MFH) is the most commonhigh grade soft tissue tumor. It occurs typically in older patients pastthe age of 50 years and is more common in men. The most commontype is the so-called storiform or pleomorphic malignant fibroushistiocytoma, followed next by the myxoid, giant cell, and inflamma-tory subtypes. The pleomorphic form is seen in patients between thethe age of 50 and 70 years, and is usually found in a deep location ina large muscle about the thigh, hip or retroperitoneal area. Thesetumors usually present with symptoms of pain along with a tumormass that has been present for at least 3 or 4 months, but sometimesthese lesions can be asymptomatic. The gross appearance of thetumor is a multinodular lesion that can have separate satellite lesionslocated within the same muscle belly, usually at the upper or lowerpole of the lesion. On MRI, the lesion may demonstrate centralnecrosis. The color is a dirty gray to reddish tan. Because this tumor
is usually high grade, it demonstrates a high index of mitotic activityand the cell types usually found are malignant fibroblasts mixedwith anaplastic pleomorphic histiocytes. This tumor has a highpotential to metastasize to the lung in about 40-45% of cases. It cango to regional lymph nodes in 10% of cases. With appropriatesurgical and adjuvant therapy, the local recurrence rate is in theneighborhood of 10-15% after a wide surgical resection. When thesetumors are located in a superficial, subcutaneous location andpresent with a size less than 5 cm, the overall prognosis is muchbetter, with only a 20% chance of metastasis to the lung. However, inthe more common, deeply located lesions that measure over 5 cm indiameter, the overall survival rate is 55%. The usual treatment for the high grade MFH is a wide surgicalresection when possible. If the tumor is too large and cannot beresected safely because of major neurovascular invasion or multiplecompartmental contamination, an aggressive high level amputation issometimes indicated. Following surgical resection, most patients
with the more aggressive lesions will be treated with adjuvantpostoperative radiation therapy, in the neighborhood of 6500 centigray to the tumor site, with a wider field of 5500 centigray outsidethe surgical site. At some institutions, patients will be treated withpreoperative radiation therapy, up to about 5500 centigray, withan additional 1000 centigray being delivered two weeks aftersurgery. The use of adjuvant chemotherapy for high grade soft tissuesarcomas is quite controversial because there is minimal data tosuggest that the prognosis is significantly improved with its use.Medical oncologists tend to discourage the use of this adjuvant,especially in older patients who cannot tolerate the high toxicitylevels of current protocols. The myxoid variant of the MFH is the second most commontype of MFH. Grossly it has a myxoid appearance and, because ofthis, the chance of local contamination at the margins (with localrecurrence) is much higher. However, the metastatic rate to the lungis only 25% giving the patient a better prognosis for survival.
The giant cell variant, occurring in large muscle groups in olderpatients, has a tendency to be a hemorrhagic tumor with a highpulmonary metastatic rate of 50%. The inflammatory MFH is alsoseen in older patients and is more common in the retroperitonealarea, with a 50% metastatic rate to the lung.
CLASSICCase #25860 year maleMFH adductorcompartmentCoronal T-1 MRI
Fibrosarcoma The soft tissue fibrosarcoma is clinically very similar to the MFH,except for the absence of malignant-appearing histiocytes. Thefibrosarcoma is less common compared to the MFH and occurs in aslightly younger age group between the ages of 30 and 55 years,with equal involvement in males and females. This tumor can bevery low grade, similar to a desmoid tumor, in which case it growsslowly and is relatively painless. The high grade lesions are fastergrowing, more painful and carry a worse prognosis. These tumorstend to affect deep fascial structures, around muscles in the area ofthe knee and thigh, followed next by the forearm and leg. Grossly,the fibrosarcoma has a firm lobulated pattern with a yellowish-whiteto tan coloration. Occasionally, there will be calcific ossifyingdeposits seen on x-ray examination. Histologically, the fibrosarcomais composed of spindle cells that form collagen fiber with varyingdegrees of mitotic activity from grade I through grade III or IV,
but there are no malignant histiocytes seen the fibrosarcoma. The treatment and prognosis depends on the grade of the tumor,with the grade I lesions behaving much like a desmoid tumor with avery slight potential for pulmomary metastases, whereas the gradeIV have a high potential for metastasis to the lung in about 50-60%of cases. It is rare to see lymph node involvement. Treatmentconsists of wide surgical resection. With the larger deep lesions,resection is usually followed by local radiation therapy to the extentof 6500 centigray, however the use of adjuvant chemotherapy isconsidered controversial. As in the treatment of MFH, chemotherapyis not usually advocated by medical oncologists.
CLASSIC Case #266 Axial T-2 MRI41 year malefibrosarcomaforearm
Dermatofibrosarcoma Protuberans The dermatofibrosarcoma protuberans is considered a low tointermediate grade fibrohistiocytic tumor characteristic in its nodularcutaneous location and occurring far more often in males then infemales, in a young to middle-aged adult population. It is mostcommonly found in the trunk or proximal extremities and can beassociated with antecedent trauma in about 15% of cases. It usuallycomes on gradually as a subcutaneous nodule that is relativelypainless and therefore patients may not present to a physician fortreatment for many years. Histologically, the tumor consists of lowgrade spindle cells without evidence of mitotic activity and lowgrade histiocytes. The spindle cell pattern is typically a storiformone, similar to the fibrosarcoma and MFH. The tumor tends to invadeinto the adjacent subcutaneous fat and skin and requires a very widesurgical resection to avoid a high local recurrence rate. The chanceof pulmonary metastasis, however, is very low (1%). With a success-ful wide resection there is no need for adjuvant therapies.
CLASSIC Case #268 30 year male with dermatofibrosarcoma protuberans on the bottom of the heel