GATA3 and breast carcinoma: CK7/CK20 expression patterns are not exclusive to either breast or gastrointestinal origin, and false-negative results may arise when biopsy specimens are small or superficial—especially in the setting of submucosal infiltration.14) GATA3, while commonly positive in breast carcinoma, has also been reported in non-breast tumors.15) Therefore, immunohistochemical results must be interpreted in the context of clinical history, imaging findings, and morphological features, rather than relied upon solely.