Nonspecificity of colon-specific antigen in adenocarcinomas. An immunohistochemical study of 422 cases.

To determine the specificity of colon-specific antigen in adenocarcinomas, routinely prepared paraffin-embedded tissue from 422 cases of adenocarcinoma were studied using a commercially available monoclonal antibody to colon-specific antigen and a standard avidin-biotin immunohistochemical technique. Positive reactivity for colon-specific antigen was very common (80% to 100%) in adenocarcinomas of the colon, distal esophagus/stomach, ovary, endocervix, endometrium, lung, pancreas, prostate, and bile ducts. Positive reactions were infrequent in adenocarcinomas of the breast (16%) and in hepatocellular carcinomas (23%). No immunoreactivity was seen in adenocarcinomas of the thyroid or in renal cell carcinomas. It is concluded that colon-specific antigen is not a colon-specific marker in adenocarcinomas. However, it may be useful in ruling out adenocarcinomas of renal or thyroid origin in certain clinical settings.