A 67-year-old woman had multiple, pinhead-sized, yellowish papules localized to her face, scalp, and neck. A previously diagnosed T-cell lymphoma of low malignancy had been treated with cytostatic drugs. Ultrastructurally the dermal infiltrate consisted predominantly of histiocytic cells in various degrees of differentiation. The cells revealed signs of high metabolic activity and contained well-developed mitochondria, rough endoplasmic reticulum, and lysosomes. Groups of worm-like bodies (comma-shape bodies) and great numbers of coated vesicles in various sizes could be regularly found. Microvillous cell processes formed close interdigitations, and desmosome-like structures occurred between adjacent cell membranes. Lipid storage was present in the form of neutral lipid vacuoles, cholesterol clefts, and myelin-like arrangements of phospholipid membranes. Some multinucleated histiocytic cells, mast cells, lymphocytes, and eosinophilic granulocytes were encountered in the infiltrate. No dermal Langerhans' cells with their characteristic granules were present. Similarities to and differences from benign cephalic histiocytosis, generalized eruptive histiocytoma, and other xanthomatous disorders are discussed.