The diagnostic utility of the triple markers Napsin A, TTF-1, and PAX8 in differentiating between primary and metastatic lung carcinomas.

Napsin A and thyroid transcription factor-1 (TTF-1) are useful biomarkers for differentiating lung adenocarcinoma from squamous cell carcinoma and also for differentiating primary lung adenocarcinoma from metastatic lung carcinoma. Pair-boxed 8 (PAX8) can help in distinguishing primary lung carcinoma from metastatic carcinomas and help to determine the primary sites of metastatic carcinomas. Immunohistochemistry for Napsin A, TTF-1, and PAX8 were performed on 193 cases of carcinoma: 50 primary lung carcinoma and 143 carcinomas from other sites. Napsin A and TTF-1 were positive in 54, 52 % of lung carcinomas cases, respectively. While in adenocarcinoma cases, their expressions were 86.7 and 83.3 %, respectively. PAX8 was negative in all lung carcinomas. TTF-1 and PAX8 were positive in 93.3 and 96.7 % of thyroid carcinoma cases and in 87.5 and 93.8 % of papillary carcinoma respectively, and both were positive in 100 % of follicular carcinoma. Napsin A was negative in all thyroid carcinomas. Napsin A and PAX8 were positive in 50 and 93.3 % of renal carcinoma cases and in 81.8 and 100 % of papillary carcinoma, 38.5 and 92.3 % of clear cell carcinoma, and 16.7 and 83.3 % of chromophobe carcinoma respectively. TTF-1 was negative in all renal carcinomas. PAX8 was positive in 80 % of ovarian carcinoma cases; 100 and 60 % of serous mucinous carcinomas, respectively. It was also positive in 100 % of endometrial carcinoma. Napsin A and TTF-1 were negative in both ovarian and endometrial carcinomas. Our data demonstrated that combined use of Napsin A, TTF-1, and PAX8 may help in differentiating between primary lung adenocarcinoma and metastatic lung carcinomas.