The congenital basal cell adenoma of salivary glands. Contribution to the differential diagnosis of congenital salivary gland tumours.

Congenital epithelial tumours of the salivary glands are very rare. The Salivary Gland Registry maintained in the Department of Pathology. University of Hamburg, contains only three cases among a total of 6,646 salivary gland tumours from the years 1965-1994. The three cases were classified as congenital basal cell adenoma, two of the parotid gland and one of the submandibular gland. Histologically, the three adenomas were similar in structure to the adult counterpart of basal cell adenoma with solid, trabecular or tubular (duct-like) patterns. In some cystic spaces of the duct-like structures PAS- and Astra blue-positive substances were secreted. On immunocytochemistry, the luminal duct-like cells showed membranous expression of cytokeratins 3, 5, 6, 7, 13 and 19. In the isomorphic basaloid cells of the solid and trabecular cell nests few cells expressed cytokeratin. On the outside of the solid cell nests there were smaller elongated myoepithelial-like cells, which expressed cytokeratin 14 and vimentin. Cytokeratins 1, 2, 4 and 18 were not expressed. The pattern of expression reflects the different stages of maturity of the tumour cells and is related to the development of the salivary glands until the end of the 3rd embryonal month with an arrest of further cell differentiation. No acinic cells, invasive growth, recurrence or metastases were observed. The differential diagnosis includes other congenital salivary gland tumours, such as hybrid basal cell adenoma-adenoid cystic carcinoma, sialoblastoma or embryoma, carcinoma, hamartoma and teratoma.