Expression of bcl-2 in salivary glands and salivary gland adenomas. A contribution to the reserve cell theory.

The bcl-2 proto-oncogene product inhibits apoptosis. It has been suggested that bcl-2 assists the survival of stem cells. Bcl-2 also plays a role in the development of adenomas. In salivary glands it is expressed in basal cells of striated and excretory ducts which may indicate that these cells are reserve cells. Acinar cells, myoepithelial cells and most luminal cells are negative for bcl-2. In basal cell adenomas and Warthin's tumors it is found predominantly in cells with basal cell differentiation. In pleomorphic adenomas bcl-2 is expressed mainly in basal cells of tubulo-ductal structures, at various degrees and patterns in solid and trabecular areas and at low degree in myxoid areas. In chondroid areas of pleomorphic adenomas, in myoepitheliomas and oncocytomas it is only focally expressed or missing. If the inhibition of apoptosis plays a significant role in the genesis of these neoplasms, then factors other than bcl-2 must be effective.