Utility and pitfalls of GATA3 immunocytochemistry for diagnosis of metastatic breast carcinoma and urothelial carcinoma on cytology specimens

GATA3 is a useful biomarker for detecting carcinomas of breast or urothelial origin on cytologic specimens. It may detect breast cancers with the triple-negative phenotype. Both cell block and smear preparations can be reliably used for the staining. GATA3-positive immunostaining is occasionally seen in other tumors, which may cause diagnostic confusion.