We read with interest the article by Komuta et al.1 showing large differences in clinical-pathological features of intrahepatic cholangiocarcinomas (ICCs) arising from columnar mucin-producing cholangiocytes lining large bile ducts versus ones arising from cuboidal non mucin-producing cholangiocytes located in or near canals of Hering, comprised of human hepatic stem cells (hHpSCs) that are lineage-restricted to hepatocytes and cholangiocytes. These results are in keeping with previous studies dealing with the pathological, epidemiological, and clinical heterogeneity of cholangiocarcinomas (CCs)2, 3 and with the biological mechanisms underlying this heterogeneity.4 Indeed, Komuta et al. demonstrated that multiple cells of origin determine CC clinical-pathological differences and suggested that mixed-ICC and cholangiolocarcinoma (CLC) are completely separate entities with respect to the pure mucin-producing ICC (muc-ICC). Recently, Nakanuma and Sato5 provided evidence that peribiliary glands (PBGs) could be involved in the origin of intraductal papillary neoplasms of the bile duct, a preneoplastic lesion of muc-ICC. This confirms that human biliary tree stem cells (hBTSCs), residing in PBGs,6 are probable cells of origin of muc-ICCs. The results by Komuta et al.,1 together with advances with respect to stem cell biology,6, 7 and the relationship between tumor types and their normal stem cell counterparts,4 enable a CCs classification based on cells of origin. Hypothetically, the mixed-ICCs originate from cells from hHpSC-derived lineages,7 whereas pure mucin-producing CCs (intra- and extrahepatic) originate from hBTSC-derived lineages. Based on the grade of maturation of the cell of origin within the two lineages, CCs can be reclassified as:
CCs with focal hepatocytic differentiation from hHpSC-derived lineages: combined hepatocellular-cholangiocarcinoma, mixed-CC, and CCL.
Pure mucin-producing CCs from hBTSC-derived lineages in PBGs or from epithelium of intra- or extrahepatic large bile ducts: hilar CC and muc-ICC.
A CCs classification based on the cell-lineages-of-origin is more coherent with current knowledge on the epidemiology and risk factors and may have important clinical implications for the definition of specific therapeutic targets.