Immunohistochemical detection of cytokeratin 18 and its neo-epitope in Warthin's tumor (adenolymphoma) of the parotid glands

An immunohistochemical method using a monoclonal antibody M30 (MAb M30), wh ich reacts with the product released by cleavage of cytokeratin IS (CK18) b y activated caspase, was used to investigate the presence and extent of apo ptosis in 36 cases of Warthin's turner (WT) of the parotid glands. The dist ribution of CK18 in WT was also determined and compared with that of the pr oduct detected by MAb M30. In WT, CK18 was observed mainly in the tumor cel ls of duct-like structures, but not in the cells of lymphatic tissues. Posi tive MAb M30 reaction products were found in luminal contents, duct-like st ructures and the cytoplasm of some macrophages in lymphatic a, eas nem the duct-like structures in WT. These findings indicated that apoptotic cells a le phagocytosed and eliminated as waste by macrophages. It is suggested tha t a mechanism which regulates the balance of proliferative activity and apo ptosis may be closely linked to the growth of WT.