An antiserum against epithelial membrane antigen has been used to stain a variety of lesions arising in the salivary glands. In normal major and minor glands staining was localised to the ductal systems. There was no evidence of myoepithelial cell staining. The mucous elements of the submandibular and sublingual glands were negative, but in the mucous elements of the minor glands there was focal cytoplasmic positivity. There was no cytoplasmic staining of serous elements in major or minor salivary glands. In pleomorphic adenomas the luminal membrane of ductal elements was strongly positive, with focal cytoplasmic positivity in some myxoid areas. In mucoepidermoid tumours both adjacent cell membranes and cytoplasm were strongly positive. The ductal structure of adenoid cystic carcinomas were clearly delineated while the pseudoducts produced by enclosed areas of stroma were negative. All mesenchymally derived tumours were negative and a tumour previously considered as a chondroma was strongly positive. The results are discussed in relation to phenotypic heterogeneity and the histogenesis of salivary gland tumours.
