Malignant melanoma of soft parts (clear cell sarcoma). A study of 17 cases, with emphasis on prognostic factors.

Seventeen cases of malignant melanoma of soft parts (clear cell sarcoma) are reported. The patients ranged from 9 to 70 years of age, but 13 were between 10 and 40 years of age. There were eight male patients and nine female patients. The most common tumor location (seven patients) was the foot, followed by the area around the knee (four patients). The usual histologic pattern was that of variably sized nests of uniform plump spindle cells with clear to pale cytoplasm separated by fine to coarse fibrous septa; however, variants with a substantial proportion of epithelioid cells, moderate to marked nuclear pleomorphism, predominantly diffuse growth, or a microcystic pattern were seen. Patient survival was relatively poor overall (median, 49 months; ten deaths due to tumor) and was determined mainly by distant metastasis (11 patients). Both survival and distant metastasis were correlated with tumor size (P less than 0.01 for patients with tumors greater than or equal to 5 cm versus less than 5 cm). Other clinical and pathologic factors, including patient age, sex, and race, tumor location, duration of symptoms, initial therapy, mitotic rate, tumor necrosis, proportion of epithelioid cells, and nuclear pleomorphism had no significant relation to survival or distant metastasis when tumor size was taken into account. Local recurrence and regional lymph node metastasis each occurred in four patients.