Use of tumour marker immunoreactivity to identify primary site of metastatic cancer.

OBJECTIVES To determine whether variations in the expression of tumour related antigens can predict the origin of tumours. DESIGN Immunohistological study of tumour marker expression in primary adenocarcinomas and respective metastatic deposits. Antibodies to the following tumour markers were used: polymorphic epithelial mucin (NCRC-11 and SM3), carcinoembryonic antigen, carcinoembryonic antigen with non-specific antigen co-specificity, CA125, CA19.9, prostate specific antigens, and thyroglobulin. SETTING Histopathology department of teaching hospital. SUBJECTS 100 pathology sections of metastatic adenocarcinoma and their related primary tumours. MAIN OUTCOME MEASURES Concordance of reactivity between primary and metastatic tumours. Reactivity profiles of tumour sites. RESULTS The correct primary site of origin was predicted in 70% (33/47) of tumours in men and 54% (27/43) tumours in women with antibodies SM3, 288, CA19.9, CA125, and PSA (men only). Specificities ranged from 68% for breast tumour to 98% for prostate tumour. CONCLUSION Use of tumour markers in patients presenting with metastatic adenocarcinoma of unknown origin can help localise the probable primary sites and reduce the need for extensive and expensive imaging techniques.