Utility of different immunostains for diagnosis of metastatic breast carcinomas in both surgical and cytological specimens

Objective A panel of immunostains is usually performed to confirm a metastatic carcinoma origin. GATA3 is a transcription factor and has been proven to be a useful marker for breast carcinoma. Other immunostains including mammaglobin (MGB), gross cystic disease fluid protein 15 (GCDFP-15), estrogen receptor (ER) and progesterone receptor (PR) are also used in diagnosing metastatic breast cancer. In this study, we aimed to compare the performance of these immunostains in the work up of metastatic breast carcinoma in both surgical and cytological specimens. Study design This study cohort was composed of 242 metastatic breast carcinomas (142 surgical and 100 cytological specimens) during a study period from October 2013 to December 2015. Immunostain results of GATA3, CK7, MGB, GCDFP-15, ER and PR and their correlations were examined. Results In surgical specimens, GATA3 and CK7 were highly expressed (88% and 87%), but MGB and GCDFP-15 showed much lower positivity rates (43% and 29%). In cytological specimens, GATA3, CK7 and MGB showed similar positivity rates to those in surgical specimens; but GCDFP-15, ER and PR showed significantly lower positivity rates than those in surgical specimens. All ER-positive cases were positive for GATA3 in both surgical and cytological specimens; however, GATA3 positivity showed a significantly stronger correlation with ER positivity in surgical specimens than in cytological specimens. Conclusions GATA3 and CK7 performed better than other immunostains to detect metastatic breast carcinoma in both surgical and cytological specimens. GATA3 expression was positively correlated with ER expression, and the correlation was stronger in surgical specimens than in cytological specimens.