Immunoperoxidase localization of keratin proteins, carcinoembryonic antigen, and factor VIII in adenomatoid tumors: evidence for a mesothelial derivation.

The histogenesis of adenomatoid tumors has been a source of controversy. Although most investigators favor a mesothelial derivation, recent ultrastructural evidence suggests that some adenomatoid tumors may be vascular neoplasms. This study reports the pattern of staining of seven adenomatoid tumors with antisera to keratin, factor VIII, and carcinoembryonic antigen (CEA), using an immunoperoxidase technique. All the tumors revealed strong cytoplasmic staining for keratin with no staining for factor VIII (an endothelial cell marker) or CEA. An identical staining pattern was evident in normal and reactive mesothelial cells. These findings support a mesothelial rather than an endothelial derivation for the tumors studied.