A study of a series of adenolymphomas showed the presence of pigmented cells in the lymphoid stroma in 85% of the cases. The pigmented cells contained light brown cytoplasmic pigment and manifested sudanophila, acid-fastness, silver reduction capacity, PAS positivity and yellow autofluorescence in ultraviolet light. The morphology, histochemical reactions and autofluorescence suggest that the pigmented cells are macrophages containing ceroid derived from breakdown of damaged organelles of the epithelial tumor cells. It is possible that these cells play a role in the elimination of undigestable pigment material present in the cystic spaces of the tumor.