Mucoepidermoid carcinoma of the salivary glands: immunohistochemical distribution of intermediate filament proteins, involucrin and secretory proteins.

Mucoepidermoid carcinomas of the salivary gland comprising low (n = 6), intermediate (n = 11) and high grade malignant (n = 11) tumors were evaluated for immunohistochemical reactivity of cytokeratin (monoclonal antibody KL1, PKK1, K8.12), vimentin, involucrin and secretory proteins (lysozyme, LY; lactoferrin, LA; alpha 1-antitrypsin, alpha 1-AT and alpha 1-antichymotrypsin, alpha 1-Ach). Keratin expression was usually confined to intense staining in epidermoid tumor cells, but was negative in almost all mucous cells. Vimentin was coexpressed with keratin only in epidermoid tumor cells. Great heterogeneity of intermediate filament proteins was found in intermediate and epidermoid tumor cells. Involucrin in epidermoid tumor cells was particularly abundant in well keratinized cells but was lacking in intermediate and mucous forming cells. The frequency of occurrence of positive staining for LY, LA, alpha 1-AT and alpha 1-Ach was relatively low in mucoepidermoid carcinoma with positive immunohistochemical staining for these secretory proteins in mucous forming tumor cells, while varying expression was observed in epidermoid tumor cells.