EVALUATION OF NAPSIN A EXPRESSION IN LUNG CANCERS AND ITS COMPARISON WITH THYROID TRANSCRIPTION FACTOR 1

Introduction: Lung cancer is the leading cause of cancer mortality in the world. With the development of new, successful treatments for adenocarcinoma, it is essential to subtype Non- Small Cell Lung Carcinoma whenever possible. Thyroid Transcription Factor-1 is a promising marker for lung adenocarcinoma but its sensitivity and specificity is limited. Napsin A is a new marker that may be useful as a part of immunohistochemistry panel to classify poorly differentiated lung carcinoma on small biopsies.

Aim: To study the expression of Napsin A in lung cancer and to compare it with TTF-1 that has already recognized as a useful marker for lung adenocarcinoma.

Methodology: This is a retrospective study. By analyzing the histopathology records during the period of 2015 - 2017, histopathological slides of biopsy proven 50 malignant lung cases were collected. Napsin A expression was tested and compared with TTF1. Results: Adenocarcinoma is the commonest type. Most common age group is 51-60 years with male female ratio is 2.7:1. Smokers have increased risk for malignancy. Napsin A and TTF1 showed similar sensitivity and the specificity of Napsin A was higher than TTF1 to lung adenocarcinoma. Napsin A showed higher sensitivity than TTF1 to exclude lung small cell carcinoma.

Conclusion: Napsin A is almost limited to adenocarcinoma, whereas TTF-1 is not so specific. Although TTF-1 is expressed in majority of adenocarcinomas, its expression is also noted in most of the small-cell lung carcinomas. Hence Napsin A can be used as an exclusionary marker for small cell carcinoma. Key words: Lung cancer, Napsin A, Small biopsy, Thyroid transcription factor 1.