Canalicular adenoma of the buccal mucosa. An ultrastructural and histochemical study

A canalicular adenoma that occurred in the minor salivary glands of the buccal mucosa in a 62-year-old black man was examined by electron microscopy and histochemistry. The ulcerated bowl-shaped tumor consisted mostly of ductlike tubules of columnar and cuboidal epithelial tumor cells which resembled intercalated duct cells ultrastructurally. Tumor cells resembling myoepithelial cells were not associated with these tubules. Less frequently, there were narrow tubules and cords adjacent to the capsule. Occasional cells in these cords contained variable amounts of microfilaments, often associated with focal densities, and thus resembled myoepithelial cells in varying stages of differentiation. Other noteworthy ultrastructural findings in this neoplasm included marked replication of the basal lamina of capillaries and the presence of a single, luminally oriented cilium in a tumor cell lining a tubule.