Differentiating metastatic breast carcinoma in the lungs from primary lung tumors and mesotheliomas is important for determining prognosis and treatment. We evaluated novel breast specific markers, androgen receptor (AR) and GATA binding protein 3 (GATA3) immunohistostaining, for this differential, and compare to other traditional markers. The specimens comprised 33 metastatic breast carcinomas to the lung, 566 primary lung tumors (170 adenocarcinomas, 157 squamous cell carcinomas, 31 pleomorphic carcinomas, 115 large cell neuroendocrine carcinomas, 43 small cell carcinomas, and 49 typical carcinoids) and 42 malignant mesotheliomas. They were analyzed by immunohistochemistry using antibodies to AR, GATA3, estrogen receptor (ER), progesterone receptor (PgR), mammaglobin, gross cystic disease fluid protein-15 (GCDFP-15). Of the metastatic breast carcinomas, immunohistostaining of AR, GATA3, ER, PgR, mammaglobin, GCDFP-15 were positive in 27 cases (81.8%), 24 cases (72.7%), 26 cases (78.8%), 13 cases (39.4%), 12 cases (36.4%), 9 cases (27.3%), respectively. Of primary lung tumors and mesotheliomas, staining of AR, GATA3, ER, PgR, mammaglobin, GCDFP-15 were positive in 18 cases (3%), 3 cases (0.5%), 4 cases (0.7%), 2 cases (0.3%), 0 case (0%), 2 cases (0.3%), respectively. Immunohistochemistry of AR and GATA3 are reliable for differentiating metastatic breast carcinoma from primary lung tumors and mesotheliomas.
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