Gata3 immunohistochemical staining is a useful marker for metastatic breast carcinoma in fine needle aspiration specimens

Aims The utility of GATA3 immunohistochemistry (IHC) as an aid to the cytological diagnosis of metastatic breast carcinoma in fine needle aspiration (FNA) specimens was investigated. Materials and Methods Cell block sections from 111 FNA cases of metastatic malignancy were stained for GATA3, including metastases from 43 breast and 44 non-mammary adenocarcinomas, 19 melanomas, 4 urothelial carcinomas and one thyroid medullary carcinoma. Sites sampled included lymph nodes (87), bone (8), liver (5), lung (6), superficial masses (4) and one pelvic mass. Results: 91% (39/43) of metastatic breast carcinoma cases were positive for GATA3. All estrogen receptor (ER) positive were also GATA3 positive cases. The majority (9/14; 64%) of ER negative and 37% (3/8) of triple negative cases were positive for GATA3. All non-mammary adenocarcinoma cases were negative with the exception of one case of metastatic pancreatic adenocarcinoma. Metastatic melanoma cases were all negative but 75% (3/4) urothelial carcinomas expressed GATA3. Conclusions GATA3 IHC staining is a useful addition to immunohistochemistry panels for FNA samples in specific settings, such as distinguishing metastatic breast from lung carcinoma or melanoma.