DISTRIBUTION OF CARCINOMA ANTIGENS CA19-9 AND CA15-3 - AN IMMUNOHISTOCHEMICAL STUDY OF 400 TUMORS

Immunohistochemical localization of antibody-defined tumor-associated antigens CA19-9 and CA15-3 was investigated in 400 malignant neoplasms from 18 organ sites. This was done to evaluate these antigens as poss ible immunohistochemical markers for determination of the origin of me tastasis of tumors of unknown primary sites. Previously, CA19-9 was wi dely used as a serum marker for pancreatic carcinoma and CA15-3 for br east carcinoma. In the present study, the avidin-biotin peroxidase com plex (ABC)-technique was used with diaminobenzidine as the chromogen. CA19-9 was highly expressed in gastrointestinal (gastric, pancreatic, colonic) adenocarcinomas and salivary gland mucoepidermoid carcinomas, but was only exceptionally positive in breast, kidney, and prostate c arcinomas. Thus, this marker may be helpful in specific clinical circu mstances to predict site of origin of metastatic adenocarcinoma. CA15- 3, often used as a serum marker for breast carcinoma, was expressed by adenocarcinomas of different origin that typically showed positive st aining in a high proportion of tumor cells. Therefore, CA15-3 appears unsuitable as a marker to evaluate the possible breast origin of metas tatic carcinoma of an unknown primary site.