Immunohistochemical staining of tenascin in Warthin's tumor and in oncocytoma.

The presence of tenascin was studied immunohistochemically in Warthin's tumor and in oncocytoma. In Warthin's tumor this extracellular matrix protein was seen in the proximity of the basement membrane zone beneath the oncocytic epithelium, in the proximity of the basement membrane of venules and of high endothelial venules, and in the reticular tissue of the lymphoid stroma. Type IV collagen was seen in the same areas as tenascin. Fibronectin was also seen in areas similar to those of tenascin and in the adjacent stroma. Tenascin was found in oncocytoma as a focal staining, and fibronectin was seen around the basement membrane and adjacent stroma. Type IV collagen was seen as a distinct staining along the basement membranes. Although the oncocytic epithelial cells in Warthin's tumor and in oncocytoma are thought to be actively proliferating cells, these two tumors differ in tenascin expression.