Role of immunohistochemistry in the subtyping of non small cell lung carcinoma

Introduction: Worldwide, lung carcinoma is the most common cancer in terms of number of cases and deaths. Lung carcinomas are broadly divided into small cell carcinoma and non-small cell lung carcinoma (NSCLC). In recent years availability of targeted therapies necessitated subtyping the NSCLC to improve the survival and quality of life. NSCLC can be subtyped by routine Haematoxylin and Eosin (H&E) stained section slides alone, poorly differentiated tumors are difficult to segregate morphologically, especially in guided biopsies, necessitating ancillary techniques like immunohistochemistry (IHC). Materials and Methods: A prospective study of two years duration (2017 and 2018) during which 100 cases of NSCLC on guided biopsies were first reported on Haematoxylin and Eosin sections and later subjected for IHC using relevant markers like CK5/6, CK7, TTF-1, Napsin-A, P63, P40, Synaptophysin and Chromogranin. Results: Out of 100 cases, after IHC, 49 were diagnosed as adenocarcinoma and 51 as squamous cell carcinoma. In adenocarcinoma positivity for CK7, TTF-1, and Napsin-A was 95%, 60% and 45% respectively. In squamous cell carcinoma positivity for CK5/6, P63 and P40 was 76%, 82% and 88% respectively. Conclusion: P40 and TTF-1 are more specific markers in our study to differentiate squamous cell carcinoma and adenocarcinoma. Keywords: Adenocarcinoma, Squamous cell carcinoma, Napsin-A, TTF-1, CK7, P40, P63, CK5/6.