The Significant Impact of Immunohistochemistry in the Classification of Lung Carcinoma on Small Biopsies

Background : There are limitations of histomorphology in the appropriate categorization of lung carcinoma where immunohistochemistry can confirm the morphological diagnosis and may add value in the poorly differentiated and undifferentiated tumors. The aim of the study was to assess the role of immunohistochemistry in classifying lung carcinoma on small biopsy samples. Methods and Material: A retrospective hospital based, observational study was conducted on cases of lung carcinoma diagnosed by core needle or bronchoscopic biopsies over a 3- year period. After evaluation of clinical findings and H&E sections, all biopsies were evaluated by immunohistochemical staining. The immunohistochemistry panel included cytokeratin cocktail, CK7, CK 20, TTF1, Napsin A, CK5/6, p40, synaptophysin, chromogranin, CD 56. Result: Out of 78 cases, the mean age was 58 +/- 11 years. Most prevalent malignancy type was adenocarcinoma (30, 38.1%). Adenocarcinoma cases were positive for CK7 (25/26, 96%), Napsin A (24/26, 92%), TTF1 (15/30, 50%) and negative for CK 20. Squamous cell carcinoma cases showed positivity for p40(18/22, 82%) and CK 5/6 (17/22.71%).Small cell carcinoma showed positivity for neuroendocrine markers synaptophysin (5/7,71%) and chromogranin(4/7, 57%) and CD 56 (6/7cases (85%).88% of small cell carcinomas,75% of adenocarcinomas and 72 % of squamous cell carcinomas were accurately diagnosed by morphology. Morphologic prediction was poor in the NSCC NOS group (0%) and poorly differentiated carcinomas (64%), which were finally, diagnosed by immunohistochemistry.In the morphologically diagnosed cases, immunohistochemistry confirmed the diagnosis. Conclusion: Thus, morphology added with immunohisto chemistry provides a crisp diagnosis thereby improving therapeutic efficacy