BACKGROUND :- Lung cancer is the leading cause of cancer-related mortality over word wide, Although the pathological diagnosis of lung carcinoma is limited as only small specimen available for diagnosis.the availability of targeted therapies has created a need for precise subtyping of non-small cell lung carcinoma . Several recent studies have demonstrated that the use of Immunohistochemical markers can be helpful in differentiating lung squamous cell carcinoma (LSCC) from lung adenocarcinoma (LAC) not on surgically resected material but also on small biopsy samples and cytology.

AIM (1) To classify the non small cell lung carcinoma into major categories like squamous cell carcinoma (LSCC) and adenocarcinoma (LAC) and other categories by applying immunohistochemicalmarker like p40 (truncated p63) and Napsin A

(2) To analyse the sensitivity and specificity of p40 and Napsin A in light of histomorphology and/or other relevant immunohistochemical markers available, using appropriate statistical tests.

Material and methods:- This study was a one and half year (18 months) prospective study from Jan 2017 to June 2018, conducted in department of pathology on patients attending the outpatient and inpatient department of TB and respiratory disease, a total of 210 bronchoscopic guided biopsies / transthoracic (CT/MRI /guided) small tissue biopsies from the patients suspected of lung malignancy were incorporated in the study. 20 corresponding resection specimens (wedge resection and lobectomy) were also included in the study for correlation of morphology and immunohistochemical findings on small biopsies.

RESULTS:-In our study IHC for both p40 and napsin –A aided in subtyping of 71.9% cases of non small cell lung carcinoma and this diagnostic accuracy was found to be statistically significant with p-value < 0.05.,on statistical analysis we found that napsin-A had a sensitivity of 90% and specificity of 80%. Also, positive predictive value and negative predictive value were seen to be 88.0% and 81.8% respectively.

Savita singh