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A case of epithelioid sarcoma of the forearm with metastasis to the lungs is reported and histological features which help in recognition of this lesion are presented.

This study concerns 65 patients with fibrohistiocytic tumors that microscopically had a bizarre and often malignant appearance. Four histologic types were recognized: atypical fibrous histiocytoma (18 tumors), malignant fibrous histiocytoma (33 tumors), malignant histiocytoma (seven tumors), and epithelioid sarcoma (seven tumors). Twenty-one of the tumors (18 malignant) evolved from the superficial tissues and 44 (29 malignant) from the deep soft tissues. Local recurrences were noted in 73% of the patients treated by local excision. Metastases occurred in 19 patients (regional lymph nodes in 13 instances and lungs in 14 instances). Five-year survival rates were 90% for the group with atypical fibrous histiocytoma, 64% for the group with malignant fibrous histiocytoma, 50% for the group with malignant histiocytoma, and 100% for the group with epithelioid sarcoma; the 10-year survival rates were 80%, 38%, 0%, and 80%, respectively. Although everyone may not agree with the concept of tissue histiocyte origin, the lesions do present a definite histologic range with recognizable transitions from the atypical through the malignant forms.

This article reviews the pathologic features and the behavior of 62 cases of a peculiar form of sarcoma that has repeatedly been confused with a chronic inflammatory processa necrotizing granulomaand a squamous cell carcinoma. The tumor occurs chiefly in young adults (median age 23 years) and most commonly affects the soft tissues of the handthe forearmand the pretibial region. It tends to grow in a nodular or multinodular manner along fascial structures and tendonsoften with central necrosis of the tumor nodules and ulceration of the overlying skin. Most of the tumors grow slowlyand many of our cases had been present for months or years prior to surgery. Microscopicallythe tumor consists of irregular nodular masses of largedeeply acidophilic polygonal cells merging with spindle cellsfrequently associated with large amounts of hyalinized collagen. Follow-up information on 54 patients (87%) revealed slowrelentless clinical course with frequent recurrence (85%) and late metastasis (30%). Cure may be achieved by wide local excision at early stage of disease.

This is a report of nine cases of epitheloid sarcoma, a term introduced recently to designate a special variant of malignant soft tissue tumor generally involving tendons, aponeuroses, and more superficial tissues of the extremities. The histologic features of this tumor, which consists of a mixture of polygonal epithelioid cells and elongated fibroblastic cells with necrotizing foci, have often misled the pathologist into diagnoses of necrotizing granuloma, malignant melanoma, angiosarcoma, or metastatic carcinoma. The tumor is definitely malignant, is difficult to eradicate by local surgical excision, and often metastasizes to lymph nodes and via the blood. The histogenesis of this tumor is still controversial, but some light and electron microscopic features suggest a possible synovial origin.

Tumor cells of three examples of epithelioid sarcoma reveal ultrastructural features characteristically found in neoplastic and, to a lesser extent, nonneoplastic fibrocytes. Their appearance is unlike that observed in rhabdomyosarcoma, liposarcoma, and neurogenic and other neoplasms with which it might be confused. The conclusion that the epithelioid sarcoma represents a fibrosarcoma does not exclude a topographic origin from synovium. Yet, if the epithelioid sarcoma is synovial it would represent either an atavistic, fibrocytic form of synovioma or neoplasm of less-differentiated fibrocytes of this structure since its cells lack pronounced cytoplasmic fenestratin, elongated filopodia, and surface deposits regarded by some as characteristic of synovioblasts. Further, pseudoacinar formation and histochemically demonstrable acid mycopolysaccharide—of the hyaluronic acid type—features also attributed to synovioblasts—were lacking in the epitheliod sarcoma. On the other hand, desmosomal attachment plates, structures not observed in synovioblasts, were noted in one epithelioid sarcoma studied.