Phagocytic plasma cells in a patient with multiple myeloma.

A female patient with IgG multiple myeloma and phagocytosing plasma cells is presented. Electron microscopical investigation showed an unusually large number of small mitochondria in the myeloma cells. In 21%, intracytoplasmic incorporation of one or more red cells or occasionally of erythroblasts or cells of the myeloid series were found. Uptake of platelets was seen rarely only. Studies of the in vitro phagocytic activity of myeloma cells did not reveal phagocytosis of opsonized bacteria or of latex particles by the malignant plasma cells.