An apocrine cystadenoma was examined with the electron microscope. Two types of cells were identified: secretory cells and basal (myoepithelial) cells. The secretory cells showed abundant granules that had the features of lipid droplets. The lumen of the cyst contained fragments of cytoplasm that appeared to be detached from the apical portions of the secretory cells. This feature suggests an apocrine type of secretory mechanism involving decapitation of the apical parts of the cells. A merocrine type of secretion was also seen. The basal myoepithelial cells showed abundant cytoplasmic filaments, most of which appeared to be tonofilaments. These cells had fewer myofilaments than those seen in normal apocrine gland cells. Annulate lamellae were not seen in this case.
(Arch Dermatol 115:194-200, 1979)