Mammary origin of metastases. Immunohistochemical determination.

Zinc-alpha 2-glycoprotein, gross cystic disease fluid protein 15, and estrogen receptors are expressed in a great proportion of breast carcinomas. These markers were investigated by immunohistochemistry in 28 metastases from breast carcinomas and for comparison on 24 metastases from other carcinomas. A group of 83 primary nonmammary tumors was also studied. Most (> 96%) breast carcinoma metastases expressed one or several markers, while all metastases of other origins were negative. This sensitive and apparently specific immunostaining proved to be of great utility in cases in which the mammary origin of metastases was difficult to establish. In four axillary lymph node metastases, it even led to the discovery of an occult homolateral breast carcinoma that was not detectable by clinical and mammographic investigations. This study indicates that the combined use of zinc-alpha 2-glycoprotein, gross cystic disease fluid protein 15, and estrogenic receptors represents a useful immunostaining technique that can help the pathologist in determining the origin of breast carcinoma metastases.