Warthin's tumor: an ultrastructural and immunohistochemical study of basilar epithelium

The cellular characteristics of the basilar epithelium in Warthin's tumor have had limited investigation. Ultrastructural examination of basal cells in 9 Warthin's tumors reveals that in addition to numerous mitochondria these cells possess a rich complement of tonofilaments. However, in three examples there are a proportion of these tonofilament-rich cells that have a narrow band of microfilaments in the peripheral cytoplasm adjacent to the basal lamina. Frozen sections of Warthin's tumor and normal salivary glands, doubly labeled with rhodamine-phalloidin for actin and monoclonal antibody 312C8-1 for cytokeratin 14, show that normal myoepithelial cells of acini and intercalated ducts have both of these filaments, as do a proportion of basal cells in the tumor. There are distinct differences in the cytokeratin polypeptide complement between normal luminal and myoepithelial cells as well as between luminal and basal cells in Warthin's tumor. Differences occur in the cytokeratin profiles between the luminal and basal cells of Warthin's tumor and comparable cells in the normal gland; however, there continue to be some similarities in the cytokeratin polypeptides of myoepithelium and the basal cells of normal salivary ducts and the basal cells of Warthin's tumor. These findings show that basal cells in Warthin's tumor are a mixed population with some capable of differentiating as myoepithelial-like cells, and that this tumor could arise from any level of the normal salivary gland duct system.