Cross-reactivity with normal antigens in commercial anti-CEA sera, used for immunohistology. The need for tissue controls and absorptions.

The demonstration of carcinoembryonic antigen (CEA) in serum and in tissue sections may be of value in diagnosis and follow-up of several malignant tumors. Anti-CEA sera, however, cross-react with normal antigens, also present in tumors. The staining patterns of three commercially produced anti-CEA sera were investigated on sections of benign and malignant tissues, using an indirect immunoperoxidase technic. All three anti-CEA sera tested showed cross-reactions. A rapid, simple, and reproducible immunoabsorption was developed. After absorption, the reactivity of the sera with normal colon mucosa and carcinomas of the colon remained positive, whereas sections of benign tissues were negative. Moreover, four of ten breast cancers, positive with unabsorbed antisera, became negative after absorption. These findings stress the importance of immunohistochemical negative and positive controls. The use of well-absorbed commercial anti-CEA sera can lead to more uniform results, exchangeability of results, and a better understanding of the value of this tumor marker.