IMMUNOHISTOCHEMICAL DIFFERENTIATION OF METASTATIC BREAST CARCINOMAS FROM METASTATIC ADENOCARCINOMAS OF OTHER COMMON PRIMARY SITES

To test the possibility of immunohistochemical differentiation of cyto statically treatable metastatic breast carcinomas from other metastati c adenocarcinomas of unknown primary site, we studied a total of 328 m etastatic adenocarcinomas including 35 bronchogenic, 26 pancreatic, 25 colonic, 39 gastric, 45 renal, 29 ovarian and 129 breast carcinomas w ith a panel of 13 commercially available monoclonal antibodies. The ex pression of gross cystic disease fluid protein 15 and/or oestrogen or progesterone receptors had a sensitivity of 0.83, a specificity of 0.9 3 and a predictive accuracy of 0.92 for carcinomas of the breast again st all other carcinomas, Excluding ovarian carcinomas, this combinatio n had a sensitivity, specificity and predictive accuracy for mammary c arcinomas of 0.83, 0.98 and 0.98, respectively. Carcinoembryonic antig en and/or cytokeratin 20 identified bronchogenic, gastric, pancreatic and colorectal carcinomas versus breast carcinomas lacking gross cysti c disease fluid protein 15 and oestrogen or progesterone receptors wit h a sensitivity, specificity and predictive accuracy of 0.82, 0.99 and 0.95, respectively. Vimentin differentiates renal cell carcinomas fro m gross cystic disease fluid protein 15 and oestrogen or progesterone receptor negative breast carcinomas with a sensitivity, specificity an d predictive accuracy of 0.93, 0.82 and 0.84. Thus, it should be possi ble to differentiate most metastatic mammary carcinomas from metastati c adenocarcinomas of other common primary sites, even if the former la ck expression of gross cystic disease fluid protein 15 and oestrogen o r progesterone receptors.