USE OF TUMOR-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 cospecificity, 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.