Lipofuscin pigmentation in pleomorphic adenoma of the palate.

This case of pleomorphic adenoma containing pigmented cells will contribute to the knowledge about pigmentation in salivary gland tumors because, to date, only a few such descriptions have been published. The pigment was examined by using histochemical and immunohistochemical methods, as well as by transmission electron microscopy. Pigment granules stained yellowish-brown with hematoxylin and eosin. The granules stained positive with Schmorl's, Ziehl-Neelsen, periodic acid-Schiff, Fontana-Masson, or Nile blue stains. Fluorescent microscopy revealed strong granule autofluorescence. Transmission electron microscopy disclosed cytoplasmic granules with homogeneous electron-dense appearance, ranging from 0.5 to 1.0 microm in dimension and arranged in diffusely distributed and aggregated patterns. The pigment was found to be lipofuscin, and the cells containing the granules were discovered to be plasmacytoid myoepithelial cells.