[2056] PAX8 Is Useful in Discriminating Metastatic Endometrioid Carcinoma with Infrequent TTF-1 and Napsin A Positivity in the Lung

Jiqing Ye, Julietta Fiscella, Sylvie Honnons, Loralee A McMahon, Qi Yang, Faqian Li, Haodong Xu. University of Rochester Medical Center, Rochester

Background: TTF-1 and napsin A have been considered as reliable biomarkers for primary lung adenocarcinoma. However, studies have shown TTF-1 is expressed in extrapulmonary carcinoma including endometrial endometrioid carcinoma (EEC) in which napsin A expression remains largely unknown. PAX8 has been reported to be positive in gynecological epithelial neoplasms including EEC but it is negative in lung adenocarcinoma. This study was to determine the expression pattern and the diagnostic value of TTF-1, napsin A and PAX8 in metastatic EEC in the lung.
Design: Fifty-one resected endometrial cancers (47 EECs, 3 serous carcinomas and 1 carcinosarcoma), as well as 4 resected and 2 biopsied metastatic EECs in the lung were retrieved. Twenty-six endometrial caners were used to construct a tissue microarray with 3 representative cores from each case. Tissue microarray as well as whole tissue sections were immunohistochemically stained with anitbodies for evaluating TTF-1 and PAX8 nuclear and napsin A cytoplasmic staining. A p value of <0.05, as determined by Fisher's exact test, was considered statistically significant.
Results: Two (33.3%) of 6 metastatic EEC were positive for TTF1 and one of 2 also expressed napsin A. Both TTF-1 and napsin A immunostains were strong and diffuse. All 6 cases showed moderate or strong and diffuse PAX8 positivity. Primary EEC of this TTF1 and Napsin A double positive metastasis was also strongly and diffusely positive for these three markers. Three of 51 primary endometrial cancers expressed TTF-1, one carcinosaroma was strongly positive with >80 positive tumor cells stained in both carcinoma and sarcoma components, and 2 ECCs exhibited 50% of tumor cells with weak to moderate TTF-1 staining. Five (9.8%) of 51 primary endometrial cancers exhibited moderate to strong napsin A staining with >80% stained tumor cells and two of 5 napsin A postive cases showed TTF-1 positivity. All these 5 cases were psotive for PAX8. Forty-eight (94.1%) of 51 primary endometrial cancers were moderately to strongly and diffusely positive for PAX8. The frequency of PAX8 positivity was significantly higher (p<0.01) than that of TTF-1 and napsin A expression in endometrial caners.
Conclusions: A small portion of metastatic EECs in the lung were TTF-1 or both TTF1 and napsin A positive and a large portion of endometrial carcinoma expressed PAX8. Infrequent TTF1 and napsin A detection in metastatic EEC could mislead to the diagnosis of lung adenocarcinoma. Combination of PAX8, TTF-1 and napsin A is powerful in separating primary lung cancer from metastatic EEC.
Category: Pulmonary

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 315, Tuesday Afternoon


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