Monoclonal antibody‐detected vimentin distribution in pleomorphic adenomas of salivary glands

To evaluate the participation of myoepithelial components in pleomorphic adenomas, an immunohistochemical study was carried out using monoclonal antibodies to vimentin. Of a total of 80 cases, 50 tumors gave positive staining, 5 tumors very slight, and 25 tumors negative staining for vimentin. Localization patterns for vimentin were divided into 3 classes: 1) vimentin staining in fibrous stromal tissue; 2) variable intensities of vimentin staining were found in the outer layers of tumor cells in tubuloductal structures (some of which were spindle cells connected to modified myoepithelial cells which also gave variable vimentin staining); and 3) modified myoepithelial cells and chondroidlike cells displayed strongly positive staining for vimentin. Typical histologic features of pleomorphic ademomas, i.e., tubulo-ductal or duct-like structures were characterized by positive vimentin staining in outer tumor cells and by a positive keratin reaction in the luminal tumor cells. In tumors devoid of stromal connective tissues and the near absence of well-developed, or modified myoepithelial cells, vimentin staining was absent.