Malignant melanoma of soft parts. A reassessment of clear cell sarcoma.

A retrospective study of 141 cases of clear cell sarcoma of tendons and aponeuroses revealed that the tumor occurred predominantly in young patients between 15 and 35 years of age, was slightly more common in female than in male patients, and originated chiefly from tendons, aponeuroses, and fascial structures of the extremities with a predilection for the feet and knees. The tumor presented as an insidiously growing mass causing pain or tenderness in slightly more than half of the patients. The preoperative duration of symptoms varied greatly, and in 29 cases the time interval between discovery of the tumor and operation exceeded 5 years. Microscopically, the tumors varied little in appearance and were composed of short fascicles of fusiform cells with a clear to granular eosinophilic cytoplasm, vesicular nuclei with prominent nucleoli, and occasional multinucleated giant cells. Melanin was demonstrated in 72% of the 92 tumors in which the Fontana or Warthin-Starry preparation for melanin was performed. S-100 protein, a neuroectodermal marker, was positive in 13 of 19 cases. Follow-up information was available in 115 patients. Thirty-four (29.6%) were alive and well with no evidence of recurrence. Twenty-four (20.9%) patients were alive with one or two recurrences, three (2.6%) were alive following pulmonary lobectomy for metastatic sarcoma, and one was alive with metastasis in the thoracic spine. Fifty-three of the 115 patients with follow-up information had died, 50 from metastatic tumor and three from miscellaneous causes. The prevailing sites of metastasis were the lung and the regional lymph nodes. The exact histogenesis remains obscure, but the presence of intracellular melanin in two-thirds of the cases supports origin from migrated neural crest cells with the capacity for producing melanin. For this reason the term, malignant melanoma of soft parts, seems preferable over the purely descriptive term of clear cell sarcoma.