Fat-storing hamartoma of dermal dendrocytes. Clinical, histologic, and ultrastructural study

A 30-year-old man is described who since birth had a peculiar symmetrical red-brown micronodular cutaneous plaque. Within the slightly raised plaque, small firm nodules were palpable. Histologic examination revealed phagocytic cells with the appearance of histiocytes between the collagen fibers of the reticular dermis. Immunohistochemical and electron microscopic examination confirmed that the cells of the plaque were dermal dendrocytes with phagocytic activities. The existence of the lesion since birth, the phagocytosis of lipid droplets by the cells, and the lack of associated metabolic disturbances suggest a fat-storing hamartoma of dermal dendrocytes that does not correspond to a known fat-storing or fat-producing tumor.