Clear cell sarcoma with melanin pigment.

A patient with a clear cell sarcoma of tendons and aponeuroses arising in the left sacral area is reported. The tumor grossly contained two black foci that had pigment with the staining characteristics of melanin on light microscopy. Electron microscopy of these areas showed the pigment to be within melanosomes. This is the second report of a neoplasm diagnosed as clear cell sarcoma in which melanin was demonstrated; the possibility that the tumor represents a soft tissue variant of malignant melanoma is discussed. It is suggested that clear cell sarcoma is a heterogeneous entity, and that a number of different soft tissue neoplasms may present with a clear cell pattern, making diagnosis and classification difficult.