<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>: o Mass in bronchus in a old chronic smoker suggest bronchogenic carcinoma. The marker of carcinoma, on immunohistochemistry, is cytokeratin.o 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. 