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.
Complete Information on this Tumor
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.
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.
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.
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.
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.
