Primary cutaneous atypical histiocytosis with possible dissemination.

Three unusual cases that were clinically suspected to be cutaneous malignant lymphomas were investigated by electron microscopy and enzyme cytochemistry. By conventional histology, a monomorphous infiltrate of medium-sized histiocytoid cells with occasional cytoplasmic vacuoles was seen. More characteristic was the ultrastructural finding of giant multivesicular bodies and pleomorphic granules in numerous neoplastic cells. These organelles seem to be closely related and to represent a market of a clinical entity. On cryostat sections some neoplastic cells were strongly positive, some weakly positive, and others negative for lysosomal enzymes (acid phosphatase, alpha-naphthyl-acetate esterase). Several cases with the same cytoplasmic structures and similarities in clinical presentations (disseminated cutaneous nodules and larger masses) and good responses to various modes of treatment (excision, x-ray irradiation, chemotherapy) have been described in the literature. However, a fatal course is also possible.