<prompt> A 56 year old Chronic smoker, mass in bronchus resected. Most useful immunohistochemical marker to make a proper diagnosis would be -CytokeratinVimentinEpithelial membrane cadherinLeucocyte common antigen  <response>: Mass in bronchus in an old chronic smoker suggest bronchogenic carcinoma. The marker of carcinoma, on immunohistochemistry, is cytokeratin.Other epithelial markers for carcinoma are :-Epithelial membrane antigen EMA:- Breast, lung and Kidneys adenocarcinoma.Carcino-embryonic antigen: - Carcinomas of GIT, pancreas, lung, breast, uterus and ovary. 