To evaluate GATA-3 immunohistochemical expression semiquantitatively in breast, gynecologic, gastric, pancreatic-biliary tract, urothelial, and vulvar/cervical squamous cell carcinomas.
GATA-3 expression was evaluated by immunohistochemistry in 198 invasive breast carcinomas on tissue microarrays. Tissue microarrays of other tissues included 144 gynecologic tumors, 28 bladder carcinomas, 63 cholangiocarcinomas, 20 pancreatic carcinomas, and 62 gastric carcinomas. Full tissue sections of 10 invasive squamous cell carcinomas were also stained. GATA-3 expression was semiquantitatively scored using an H-score method. H-score greater than 10 was considered a positive result.
Of 186 breast carcinomas, 95% were positive (mean H-score of 217). GATA-3 expression was uncommon in 139 nonsquamous gynecologic tumors, with often weak reactivity (mean H-score <50) seen in 18% of endocervical, 7% of endometrial, and 10% of ovarian tumors. Six (60%) of 10 squamous cell carcinomas expressed GATA-3 (mean H-score of 102). Of 22 urothelial carcinomas, 95% expressed GATA-3 (mean H-score of 170). A few cholangiocarcinomas (3%), pancreatic adenocarcinomas (10%), and gastric carcinomas (2%) weakly expressed GATA-3 (mean H-score <50).
Strong GATA-3 expression is a reliable marker of primary breast carcinoma in the appropriate clinical context. GATA-3 reactivity in around 70% of triple-negative breast carcinomas is also clinically useful. Significant reactivity in gynecologic squamous cell carcinomas suggests that GATA-3 alone cannot reliably distinguish these tumors from urothelial carcinoma.