[Pigment-free clear-cell sarcoma]

Clear-cell sarcoma of tendons and aponeuroses is an infrequent soft tissue sarcoma. Although this sarcoma is now accepted as a clinico-pathological entity and is well-defined clinically, questions on the histogenesis are still under discussion. Because of the possible presence of melanin pigment the idea was put forward that these tumors may be soft tissue melanomas. The authors studied a clear-cell sarcoma without melanin pigment and found at the ultrastructural level that the tumor cells often showed a basal lamina-like material in the vicinity of their cell membranes and were inclined to wrap around extracellular structures. They were in part connected to another by desmosome-like junctions and occasionally contained membrane-bound dense bodies resembling neurosecretory-type granules. Pinocytosis and glycogen were lacking. The results of electron microscopic examination showed this tumour to be closer to the malignant schwannoma rather than melanoma: histogenetically it is obviously linked to the neural crest.