Diagnostic immunohistochemistry of cutaneous metastatic breast carcinoma: a statistical analysis of the utility of gross cystic disease fluid protein-15 and estrogen receptor protein.

For accurate classification of cutaneous metastatic carcinoma, reliable tumor-specific immunohistochemical markers would be valuable. Our purpose was to analyze the sensitivity, specificity, and positive predictive value of gross cystic disease fluid protein-15 (GCDFP-15) and estrogen receptor protein (ERP) for diagnosing cutaneous metastatic breast carcinoma. Tissue sections from 68 consecutive cases of cutaneous metastatic carcinoma were stained for GCDFP-15 and ERP. Hematoxylin-eosin-stained slides and immunostained slides were reviewed in a blinded fashion before retrospective chart review to ascertain the underlying primary tumor type. Of 42 cases of cutaneous metastatic breast carcinoma, 30 were positive for GCDFP-15. Of 41 cases of metastatic breast carcinoma, 30 were positive for ERP. Calculated sensitivity, specificity, and positive predictive value for GCDFP-15 for diagnosing cutaneous metastatic breast carcinoma were 71%, 91%, and 94%, respectively, and 73%, 100%, and 100% for ERP, respectively. Combined values of these indices for both stains were 83%, 91%, and 95%, respectively. GCDFP-15 and ERP are valuable markers for cutaneous metastatic breast carcinoma and should be used in combination.