Utility of Napsin-A in diagnosis of non-small cell lung carcinomas and its addition with thyroid transcription factor-1 (TTF-1) in small biopsies of lung: Does it help in morphologically challenging situations?

Abstract

Background: Lung cancer is the leading cause of cancer-related deaths in the world. Primary lung carcinomas were being divided simply as small cell lung carcinoma (SCLC) and non-small cell lung carcinoma (NSCLC) in recent past as the chemotherapy offered in NSCLC was not majorly different in the various subtypes. With the advent of targeted therapy, the management of primary lung adenocarcinomas (PLA) and squamous cell carcinomas (SqCCs) became divergent and hence a stringent separation of the two subgroups is imperative. This study was designed to see whether inclusion of immunohistochemistry (IHC) for Napsin-A in the panel of CK7, CK20, p40, and thyroid transcription factor-1 (TTF-1) improves the diagnostic rates of lung adenocarcinomas. Materials and Methods: A total of 56 cases of primary lung malignancies were studied and subtyped, based on Hematoxylin and Eosin stained slides along with IHC for CK 7, CK 20, p40, TTF-1, and Napsin-A. NSCLC was divided into five groups-PLA, SqCC, NSCLC–favor adenocarcinoma, NSCLC–favor SqCC, and NSCLC–not otherwise specified (NOS). Results: Out of the total, 38 cases were diagnosed to be NSCLC. Of these 38, only 55% cases were diagnosed using histomorphology alone. The rest required immunohistochemical stains for classification. The NSCLC-NOS group comprised 11% in this study. It was observed that by including Napsin-A in the panel, 01/04 (25%) cases in NSCLC-NOS group could be included in NSCLC–favor adenocarcinoma group. Conclusions: This study finds that Napsin-A labels additional cases as adenocarcinomas in NSCLC-NOS group. Napsin-A is more sensitive but less specific than TTF-1 in diagnosis of PLA and has a definite use, in conjunction with TTF-1 to classify NSCLC.