Value of GCDFP-15 (BRST-2) as a Specific Immunocytochemical Marker for Breast Carcinoma in Cytologic Specimens

The diagnosis of metastatic mammary carcinoma by morphologic criteria alone can be difficult, depending on the site of metastasis and state of cell differentiation. Numerous histopathologic studies have shown GCDFP-15 (BRST-2) to be a specific marker for breast cancer in surgical specimens. To date, no studies have been done to evaluate its utility in cytologic preparations. To evaluate the usefulness of GCDFP-15 as a marker in the cytologic diagnosis of breast carcinoma, we studied 23 cases of mammary carcinoma and compared them with 20 cases of tumors of nonmammary origin (lung, ovary, liver, colon, stomach and bladder). "Bench top" fine needle aspirates from unfixed surgical specimens of breast carcinoma, cytocentrifuge samples from body cavity fluids and cerebrospinal fluids with morphologically proven metastatic carcinoma were studied. Expression of BRST-2 was found in 56.5% of primary and recurrent or metastatic breast carcinomas. All the nonmammary carcinomas studied were negative. Staining was found to be strongly dependent on the means of cell fixation. Slides fixed in 10% formalin and Bouin's solution gave optimal results. Except in two cases, which showed focal immunostaining, all specimens fixed in alcohol were negative. Our results support the diagnostic value of GCDFP-15 in recognizing tumors of breast origin and suggest that in clinical situations in which metastatic breast carcinoma is suspected, a portion of the cytologic specimen should be fixed with an optimal fixative for BRST-2 detection.