COEXPRESSION OF CYTOKERATIN AND VIMENTIN INTERMEDIATE FILAMENTS IN BENIGN AND MALIGNANT SWEAT GLAND TUMORS

The coexpression of cytokeratin and vimentin intermediate filaments ha s been immunohistochemically evaluated in 124 benign and malignant swe at gland tumors of various types in comparison to normal sweat glands. In addition, all neoplasms have been stained by an antibody to alpha- smooth muscle actin. Epithelial cells reacted with the pan-cytokeratin antibody 1u-5. In normal sweat glands, vimentin immunoreactivity was restricted to myoepithelial cells and to some cells of the coiled duct . In benign sweat gland tumors (n = 88), coexpression of vimentin and alpha-smooth muscle actin was frequently found in basal cells of neopl asms considered to differentiate towards the secretory coil of the ecc rine or apocrine gland. These included eccrine spiradenoma, apocrine c ystadenoma, hidradenoma papilliferum, syringocystadenoma papilliferum, and cylindroma. Thus, in these tumors, vimentin-reactive cells corres ponded to myoepithelial cells. Vimentin-positive cells were also found in 14 of 36 sweat gland carcinomas, including 1 case of sclerosing sw eat duct carcinoma, 1 case of porocarcinoma, 4 cases of eccrine adenoc arcinoma, 1 case of mucinous eccrine carcinoma, and 5 cases of apocrin e adenocarcinoma. Co-expression of vimentin and alpha-smooth muscle ac tin was observed in some cells of eccrine and apocrine adenocarcinomas . Therefore, in these neoplasms, some vimentin-positive cells appear t o represent myoepithelial cells. In contrast, vimentin-positive cells in all other malignant tumors did not express alpha-smooth muscle acti n. Our results indicate that coexpression of cytokeratin and vimentin may be frequently found in a variety of benign and malignant sweat gla nd tumors. In the majority of these neoplasms, vimentin-positive cells correspond to myoepithelial cells. Because vimentin is not specific f or myoepithelial cells, additional stains for alpha-smooth muscle acti n should be performed to prove the myoepithelial nature of vimentin-po sitive cells.