Coexpression of vimentin, cytokeratin and S-100 in monomorphic adenoma of salivary gland; value of marker studies in the differential diagnosis of salivary gland tumours.

An unusual coexpression of glial fibrillary acid protein (GFAP), keratin and vimentin occurs in pleomorphic adenoma of salivary gland. We designed this study to see if coexpression of the markers was also present in monomorphic adenoma of the salivary gland and whether monomorphic adenoma could be distinguished from other salivary gland tumours by marker studies. Immunocytochemical markers were used on fine needle aspiration samples from four cases of monomorphic adenoma, two cases of oncocytic adenoma, three cases of adenoid cystic carcinoma and four cases of pleomorphic adenoma. While positivity for cytokeratin, vimentin and S-100 was consistently found in all cases of monomorphic adenoma, only cytokeratin was expressed in adenoid cystic carcinoma. In pleomorphic adenoma, GFAP, cytokeratin and vimentin were coexpressed while in cases of oncocytic adenoma none of the markers was localized. Thus, it appears that by using a combination of GFAP, cytokeratin, vimentin and S-100 a distinction between these neoplasms may be possible. However, a larger study is needed to establish the usefulness of this approach.