Immunohistochemical detection of cytokeratin 18 and its neo-epitope in human salivary glands and pleomorphic adenomas.

An immunohistochemical method using a monoclonal antibody M30 (MAb M30), which reacts with the product released by the cleavage of cytokeratin 18 (CK18) by activated caspase, was used to investigate the extent of apoptosis in human salivary glands and pleomorphic adenomas. The distribution of CK18 in the salivary glands and adenomas was also determined and compared with that of the product detected by MAb M30. CK18 was detected in the cytoplasm of serous acinar and ductal cells in normal human salivary glands. In pleomorphic adenomas, CK18 was observed mainly in the tumor cells of duct-like structures, but not in those of myxomatous or chondroid tissues. Positive MAb M30 reaction products were found in the cytoplasm of acinar cells in the restricted lobules of normal salivary glands and in the luminal contents of duct-like structures in pleomorphic adenomas. These results suggest that a mechanism which suppresses apoptosis may be linked to the growth of human pleomorphic adenomas.