Immunoprofile of mucoepidermoid carcinomas of minor salivary glands. Because the data on the antigenic phenotype of mucoepidermoid carcinoma (MEC) are incomplete and somewhat disparate, 45 MECs were evaluated immunohistochemically for low- and high-molecular-weight keratins, vimentin, glial fibrillary acidic protein, smooth muscle actin, and S-100 protein. Tumors stained uniformly for keratins and, on occasion, focally for vimentin. Tumors were nonreactive with antibodies to glial fibrillary acidic protein and, with few exceptions, to muscle-specific actins and S-100 protein. Clear cell and papillary histologic variants were seen as potential diagnostic pitfalls. If used with hematoxylin-and-eosin-stained sections, limited potential is seen for this antibody panel in surgical pathology. Myoepithelial cell-associated antigens are expressed to a very limited extent in MECs. 