True histiocytic lymphoma.

An 86-year-old man had true histiocytic lymphoma of the skin. Diagnosis was established by the following findings: (1) typical histological features, (2) lack of receptors on tumor cells for immunological surface markers, and (3) active phagocytic function. Electron microscopic studies indicated cytoplasmic multivesicular bodies in the tumor cells. Multivesicular bodies have been reported in histiocytic proliferative disorders and may be of diagnostic value in cases of true histiocytic lymphoma.