Wang T, et al. - Resected intrahepatic cholangiocarcinomas (ICCs) with targeted next-generation sequencing by MSK-IMPACT were identified and assessed by the experts in order to determine the distinct histomorphological features affiliated with IDH1 mutation in ICC. Data were gathered for histology type, mucin production, necrosis, fibrosis, cytoplasm cell shape (low cuboidal, plump cuboidal/polygonal, and columnar), and architectural pattern (anastomosing, tubular, compact tubular, and solid), blinded to IDH status. Since all IDH1-mutant tumors were of small duct–type histology, the assessment was restricted to 101 small duct–type tumors. The mutated IDH1 (mIDH1) cases were more inclined to have a plump cuboidal/polygonal shape and geographic-type fibrosis, whereas IDH1 wild-type was more prone to have a low cuboidal shape. With no meaningful variation in the distribution of architectural patterns, both groups (mIDH1 and IDH wild-type controls) were predominantly architecturally heterogeneous. Hence, in comparison with IDH wild-type tumors, plump cuboidal/polygonal cell shape and a geographic-type pattern of intra-tumoral fibrosis was more often noticed in mIDH1, however, IDH1 mutation was not correlated with a distinct histoarchitectural pattern.