Ultrastructure of the basal cell adenoma of parotid gland.

Electron microscopic examination of two classical examples of so-called basal cell adenoma of parotid gland disclosed four distinct cellular types: the squamous epithelial cells with tonofilaments and prominent desmosomes predominantly located at the central portion of neoplastic mass; the basally located secretory cells with numerous secretory granules; the occasional intermediate cells with scanty cytoplasmic microfilaments; and the peripherally situated attenuated myoepithelial cells. The neoplastic clusters are surrounded by highly replicated basal laminae with microfibrils in their interstices. This information about its component cells suggests that basal cell adenoma arises from the secretory duct, in particular the intercalated duct, of the parotid gland. The term basal cell adenoma appears appropriate for its designation. It is interesting that the secretory cells and the multilayered basal laminae illustrated in the present study are reportedly seen in adenoid cystic carcinoma of the salivary gland; this finding would suggest a common cellular origin for these two neoplasms.