Clear cell carcinoma of the salivary gland.

A rare case of primary clear cell carcinoma of the salivary gland is described, and the literature is reviewed. All primary clear cell tumors of the salivary glands are at least low-grade carcinomas. Morphologically, these tumors can be divided into two variants: bimorphic and monomorphic clear cell carcinomas. The bimorphic variant, of which the present case is an example, is morphologically unique and is composed of tubules lined by an inner layer of eosinophilic cells and an outer layer of clear cells. The monomorphic variant is composed of solid nests and cords of clear cells. The clear cells in both variants are nonmucinous and may or may not contain abundant glycogen. The clear cells in one bimorphic tumor showed features of myoepithelial differentiation ultrastructurally, but no such features were found in several cases of monomorphic tumor similarly studied. However, a close histogenetic relationship between these two tumor types is suggested by the occurrence of tumors that contained elements of both.