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Epithelioid sarcoma - Foot and Ankle

Summary

The tumor mainly afflicts young adults, its principal sites are the fingers, hands, and forearms. The next most common site is the distal lower extremity, including the leg, ankle, and foot, followed by the proximal upper extremity. Epithelioid sarcoma is the most common soft tissue sarcoma in the hand and wrist, followed by alveolar rhabdomyosarcoma and synovial sarcoma.

Most patients are young adults, with 75% percent of cases occurring in persons under 40, but children and the elderly may be affected.
The tumor may present as a small, firm superficial or deep nodule or a focal cluster of nodules. This tumor is frequently misdiagnosed as a skin condition, warts, or corns, and a correct diagnosis may be delayed with serious medical and legal consequences.
Contrast-enhanced MRI and PET CT imaging of the entire limb is essential to detect the complete extent of the disease and locate the frequent local and regional metastases.
For surgically controllable disease, surgical removal with a wide margin is mandatory.
Complete Information on this Tumor
Introduction and Definition: 

Epithelioid sarcoma is another challenging and deadly tumor worthy of special consideration. Although this sarcoma is generally rare, the most common location is the distal upper and lower extremities, with approximately 15% of all cases located in the distal lower extremity. The tumor grows and spreads along lymph and vascular channels as well as tendon sheaths, leading to more generalized swelling and a permeative mass.

Incidence and Demographics: 
Most patients are young adults, with 75% percent of cases occurring in persons under 40, but children and the elderly may be affected. Men are affected more commonly than women.
Symptoms and Presentation: 

The tumor may present as a small, firm superficial or deep nodule or a focal cluster of nodules. Regional multifocal presentation is an unusual characteristic displayed by this tumor. This tumor is frequently misdiagnosed as a skin condition, warts, or corns, and a correct diagnosis may be delayed with serious medical and legal consequences. About one half of the tumors are not painful. The tumor occurs in both subcutis and deeper tissues. When located in the subcutis, it usually presents as a firm nodule that may be solitary or multiple, has a calluslike consistency, and is often described as a “woody hard knot” or :firm lump” that is slow growing and painless. Nodules situated in the dermis are often elevated above the skin surface and frequently become ulcerated weeks or months after they are first noted. Such lesions are often erroneously diagnosed as an “indurated ulcer”, “draining abscess”, or “infected wart” that fails to heal despite intensive therapy. The majority of tumors are 3 to 6 cm in diameter.

X-Ray Appearance and Advanced Imaging Findings: 
Roentgenogram reveals mostly a soft tissue mass with an occasional speckeled pattern of calcification, and with infrequent cortical thinning and erosion of underlying bone . Contrast-enhanced MRI and PET CT imaging of the entire limb is essential to detect the complete extent of the disease and locate the frequent local and regional metastases.
Differential Diagnosis: 
Differential Diagnosis The frequency with which the tumor is mistaken for a benign process is a result of its deceptively harmless appearance during the initial phase of the disease. Superficially locate tumors of small size with a nodular or multinodular pattern are likely to be mistaken for an inflammatory process. Neoplasms arising from the tendons can be mistaken with synovial sarcoma. Distinction can be successfully accomplished if attention is paid to the persistent absence of a biphasic pattern, pseudoglandular structures and intracellular mucin, as well as the larger size and prominent eosinophilia of the tumor cells. Dermal involvement and ulceration are much more common with epithelioid sarcoma than with synovial sarcoma.
Preferred Biopsy Technique for this Tumor: 
Incisional
Histopathology findings: 
Pathological Findings Gross inspection usually shows the presence of one or more nodules measuring 0.5 to 5 cm in diameter. The cut surface has a glistening gray-white or gray tan mottled surface with focal yellow or brown areas caused by focal necrosis or hemorrhage. The principal microscopic characteristics are the distinct nodular arrangement of the tumor cells, their tendency to undergo central degeneration and necrosis, and their epithelioid appearance and eosinophilia. The nodular pattern, probably the most conspicuous single feature of epithelioid sarcoma, varies somewhat; in some tumors the nodules are well circumscribed; in others they are less well defined and are often compacted into irregular multinodular masses. Necrosis of the tumor nodules is a common finding; it is most prominent in the center of the nodules and at times is associated with hemorrhage and cystic change. When tumor spreads within a fascia or aponeurosis, it forms festoonlike or garlandlike bands punctuated by areas of necrosis. The constituent cellular elements range from large ovoid or polygonal cells with deply eosinophilic cytoplasm, suggesting a rhabdomyosarcoma or malignant rhabdoid tumor, to plump spindle-shaped cells reminiscent of fibrosarcoma or malignant fibrous histiocytoma. In some of the latter tumors the spindle cell pattern may predominate and may obscure the characteristic epithelioid features and nodularity. Cytogenetic analysis of an epithelioid sarcoma cell line revealed a karyotype of 64 to 66 chromosomes with extensive numerical and structural rearrangements and up to 24 marker chromosomes. Immunohistochemical findings The cells show coexpression for low-molecular-weight (45 kd and 54 kd) and high- molecular- weight (57 kd) cytokeratin, vimentin, and epithelial membrane antigen. Ultrastructural findings Most investigators report polygonal and spindle shaped cells with ovoid, indented nuclei having small amounts of marginally places chromatin. The cytoplasm contains arrays of rough endplasmic reticulum, a prominent Golgi apparatus, and free ribosomes as well as occasional mitochondria, lysosomes, and droplets of osmophilic material. Intermediate filaments are a common and striking feature. They may be arranged longitudinally as in myofibroblasts or more often from paranuclear masses or whorls, a feature that probably accounts for the voluminous cytoplasm and the striking epithelioid appearance and eosinophilia of the tumor cells. Flow cytometric DNA analysis revealed diploid or hyperploid and aneuploid DNA content.
Treatment Options for this Tumor: 
For surgically controllable disease, surgical removal with a wide margin is mandatory. Local and regional metastasis may necessitate amputation. Adequate treatment requires early radical excision or amputation if the primary tumor is situated in the fingers or toes. Amputation should also be considered as treatment for recurrent growth, but does not seem to offer any benefit to patients with distant metastasis. Regional lymph node dissection should be included among the therapeutic modalities because lymph node metastasis is a fairly common occurrence in epithelioid sarcoma. In all cases surgical treatment should be combined with radiotherapy and multiagent chemotherapy over a prolonged period.
Outcomes of Treatment and Prognosis: 
The local recurrence rate is approximately 35% and the rate of distant metastasis is about 40%, with the regional lymph nodes and lungs being the most common metastatic sites. Metastasis to regional lymph nodes occurs in 25% of cases. Five and ten year survival is 70% and 42%. Prognosis depends on various factors, chiefly the sex of the patient, the depth of the tumor, the number of mitotic figures, and the presence or absence of hemorrhage, necrosis, and vascular invasion. Moreover, tumors in the distal extremities have a more favorable prognosis than those in the trunk and proximal portions of the limbs.
Special and Unusual Features: 
The potential of the tumor to recur and metastasize is clearly evident. Most common sites of sites are lymph nodes and the skin, and the scalp. Multiple recurrences, often a result of marginal resection are a characteristic feature of the tumor. The recurrent tumor generally presents as confluent nodules in the dermis or along tendons and fascial structures at or near the original tumor site. Recurrence generally develops within first year after diagnosis, but may be late. Metastases may manifest before detection of the primary tumor.
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