Salivary gland basal cell and canalicular adenomas: Immunohistochemical demonstration of myoepithelial cell participation and morphogenetic considerations

Objective. - To evaluate cellular composition of salivary gland adenomas using 3 monoclonal antibodies that recognize a smooth muscle phenotype confirmed to be sensitive for myoepithelial differentiation. Design. - Immunohistochemical evaluation of 25 salivary gland basal cell and canalicular adenomas. Setting. - Archival pathology material from the files of Henry Ford Hospital, Detroit, Mich, and the University of California at San Francisco. Results. - All basal cell adenoma variants exhibit some degree of myoepithelial cell participation with periductal, epithelioid, and spindled (stromal-like) morphologic structures. Only the canalicular adenomas, even if mixed with trabecular and solid patterns, are devoid of staining with these 3 antibodies, suggesting an adenoma composed exclusively of ductal luminal cells. Conclusions. - There is an overlapping histomorphologic and common cellular composition of the basal cell adenoma variants with other recognized adenomas, such as pleomorphic adenoma and myoepithelioma. Relative differentiation toward 3 cell phenotypes (ductal luminal, basal, and myoepithelial) and the character of extracellular matrix production in varying proportions by the neoplastic myoepithelial cells distinguishes the spectrum of salivary gland adenomas identified in current classification schemes.