[1857] Usefulness of Napsin A and TTF-1 in Discriminating Metastatic Carcinoma from Primary Adenocarcinoma of the Lung

J Ye, JJ Findeis-Hosey, LA McMahon, Q Yang, JL Yao, F Li, H Xu. University of Rochester Medical Center, Rochester

Background: The differential diagnosis between metastatic and primary lung carcinoma is a frequent perplexity. TTF-1 has been considered as a reliable marker to distinguish between primary adenocarcinoma (AC) and metastasis of the lung. However, recent studies have shown that TTF-1 can be detected in extrapulmonary ACs, which makes the interpretation diffcult in certain cases. Fortunately, napsin A has been reported to be highly expressed in the lung ACs. The aim of this study was to determine if immunohistochemical detection of napsin A and TTF-1 can be powerful in discriminating primary lung AC from metastasis.
Design: Twenty-nine resected metastatic carcinomas of the lung metastatic from 7 colonic ACs, 10 conventional renal cell carcinomas (RCCs), 3 papillary or Hürthle cell carcinomas of thyroid, 1 endocervical AC, 1 ovarian endometrioid carcinoma, 1 prostatic ACA, 2 hepatocellular carcinomas, and 2 adrenocortical carcinomas and 2 breast carcinomas along with tissue microarrays (TMA) of 121 the lung ACs, and 92 clear cell, 15 papillary and 4 chromophobe RCCs and 4 oncocytomas were immunohistochemically studied using antibodies against TTF- and napsin A. Nuclear and cytoplasmic staining for TTF-1 and napsin A were considered positive, respectively, and the percentage of positively stained cells was recorded along with intensity (graded as weak, moderate, or strong). A p value of <0.05, as determined by Fisher's exact test, was considered statistically significant.
Results: Three of 7 metastatic colonic AC showed weak to moderate and patchy nuclear staining for TTF-1 in 5% to 20% of the tumor cells; one of 10 clear RCC, 1 ovarian carcinoma and 1 prostatic AC also exhibited 5% to 30% of tumor cells weakly to moderately positive for TTF-1. Reactive type II pneumocytes were strongly positive for TTF-1. All cases were negative for napsin A. In the lung AC, napsin A and TTF-1 were detected in 85.9% (104/121) and 81.0% (98/121), respectively and the sensitivity between the two was not statically different. Papillary RCCs were positive for napsin A (>80% tumor cells, moderate to strong) in 12 of 15 cases (80%) and all other renal epithelial neoplasms were negative for napsin A. TTF-1 was not detected in all cases in the RCC TMA, including oncocytomas.
Conclusions: This is the first time to report that TTF-1 is detected in both clear cell RCC and prostatic AC metastatic to the lung. Combined TTF-1 and napsin A immunostains are more powerful in separating the primary lung AC from metastasis.
Category: Pulmonary

Monday, March 22, 2010 2:45 PM

Platform Session: Section E, Monday Afternoon

 

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