Immunohistochemical expression of epidermal growth factor receptor in salivary gland tumours

Immunohistochemical localization of epidermal growth factor receptor (EGFR) in normal salivary glands and tumours (108 cases) was studied using a monoclonal antibody. In the normal salivary glands, EGFR was occasionally detected in ductal segments of intercalated, striated, and excretory ducts, but not in acinar cells. The frequency of positive EGFR staining in salivary gland tumours was not high: pleomorphic adenoma, 33.8%; mucoepidermoid tumour, 25.0%; adenolymphoma, 44.4%; and sialoadenocarcinoma, 66.6%. Pleomorphic adenomas showed positive staining for EGFR on the luminal side of luminal cells and in squamous metaplastic cells of tumour tissue. Some modified myoepithelial cells were also reactive whereas outer spindle tumour cells were unstained. Adenolymphomas regularly exhibited positive EGFR staining in the cell membrane; mucoepidermoid carcinoma displayed positive staining in cell membranes in epidermoid tumour cells and cytoplasmic staining in mucous-secreting tumour cells. Sialocarcinomas revealed cell membrane staining and whole cytoplasmic staining for EGFR. The immunohistochemical localization of EGFR could be classified into two types, one the cell membrane-positive type found in epithelial tumour cells, and the second the cytoplasmic positive type seen in normal ductal cells, the luminal tumour cells of pleomorphic adenomas and mucous-secreting tumour cells.