<prompt> Which is risk factor for cholangiocarcinoma ?ObesityPrimary sclerosing cholangitisSalmonella carrier stateHBV infection  <response>: Ans. is b i.e., Primary sclerosing cholangiocarcinoma Cholangiocarcinoma o Cholangiocarcinoma is malignancy of the biliary tree, arising from bile ducts within or outside the liver. o Risk factors : - i Primary sclerosing cholangitis ii Congenital fibropolycystic disease of the biliary system caroli disease, choledochal cyst. iii Exposure to thorotrast. iv Opisthorchis sinensis infection. Pathology o Cholangiocarcinoma are adenocarcinoma arising from bile ducts epithelium. o Most are well to moderately differentiated. o Markdly desmoplastic, with dens collegenous stroma separating the glandular elements. o Cells are not bile stained, because bile is synthesized by hepatocytes and not by bile duct epithelium. 