GATA-3 is superior to GCDFP-15 and mammaglobin to identify primary and metastatic breast cancer.

Purpose: Despite numerous studies on the utility of GATA-3 as breast cancer marker, its comparison with other breast markers, its concordance between primary and metastatic tumors and its expression in primary cancers from sites with frequent breast metastases remains unclear.

Methods: To address these questions, totally 993 invasive breast cancers (IBC), 254 paired nodal metastases, 23 distant metastases, and 208 lung carcinomas were included. GATA-3 expression was analyzed by immunohistochemistry and compared to other breast markers [gross cystic disease fluid protein 15 (GCDFP-15) and mammaglobin (MGB)].

Results: GATA-3 was expressed in 82.5% of IBC, predominantly in luminal (93.9%), and lower in non-luminal cancers [59.6% of HER2 overexpressing (HER2-OE) and 38.1% of triple negative breast cancer (TNBC) subtypes]. GATA-3 identified more IBC than GCDFP-15 (23.9%) and MGB (46.6%). However, MGB showed a comparable sensitivity for non-luminal cancers to GATA-3. Combining MGB and GATA-3 improved sensitivity for both HER2-OE (80.8%) and TNBC cases (55.4%). GATA-3 showed a high sensitivity for nodal metastases and distant metastases, with good concordance with primary tumors. GATA-3 was expressed in 1.0% of lung carcinomas, with sensitivity and specificity of 82.5 and 99.0% in differentiating IBC and lung carcinoma.

Conclusions: GATA-3 expression was the highest in luminal breast carcinomas, and showed higher sensitivity than GCDFP-15 and MGB. However, in the poorly differentiated IBC, its utility was still limited. One should be aware of the possible GATA-3 expression in lung carcinomas.