Comprehensive genetic analysis of cholangiolocellular carcinoma with a coexistent hepatocellular carcinoma-like area and metachronous hepatocellular carcinoma

Integrated analyses of the genetic and clinicopathological features of cholangiolocarcinoma: cholangiolocarcinoma may be characterized by mismatch-repair deficiency

Cholangiolocarcinoma (CLC) is a primary liver carcinoma that resembles the canals of Hering and that has been reported to be associated with stem cell features. Due to its rarity, the nature of CLC remains unclear, and its pathological classification remains controversial. To clarify the positioning of CLC in primary liver cancers and identify characteristics that could distinguish CLC from other liver cancers, we performed integrated analyses using whole-exome sequencing (WES), immunohistochemistry, and a retrospective review of clinical information on eight CLC cases and two cases of recurrent CLC. WES demonstrated that CLC includes IDH1 and BAP1 mutations, which are characteristic of intrahepatic cholangiocarcinoma (iCCA). A mutational signature analysis showed a pattern similar to that of iCCA, which was different from that of hepatocellular carcinoma (HCC). CLC cells, including CK7, CK19, and EpCAM, were positive for cholangiocytic differentiation markers. However, the hepatocytic differentiation marker AFP and stem cell marker SALL4 were completely negative. The immunostaining patterns of CLC with CD56 and epithelial membrane antigen were similar to those of the noncancerous bile ductules. In contrast, mutational signature cluster analyses revealed that CLC formed a cluster associated with mismatch-repair deficiency (dMMR), which was separate from iCCA. Therefore, to evaluate MMR status, we performed immunostaining of four MMR proteins (PMS2, MSH6, MLH1, and MSH2) and detected dMMR in almost all CLCs. In conclusion, CLC had highly similar characteristics to iCCA but not to HCC. CLC can be categorized as a subtype of iCCA. In contrast, CLC has characteristics of dMMR tumors that are not found in iCCA, suggesting that it should be treated distinctly from iCCA. © 2024 The Pathological Society of Great Britain and Ireland.

Distinctive clinicopathological features and KRAS and IDH1/2 mutation status of cholangiolocellular carcinoma

AIM

Cholangiolocellular carcinoma (CLC) is classified as a subtype of combined hepatocellular cholangiocarcinoma with stem-cell features (CHC-SC) in the latest World Health Organization classification. This subclassification of CHC-SCs is controversial and the relevance of such classification is unclear.

METHODS

We analyzed a series of CHC-SCs and intrahepatic cholangiocarcinoma (iCCA) to clarify the clinicopathological features and mutational status of each tumor.

RESULTS

Background liver disease, fibrosis stage, microvascular invasion, nodal metastasis, and IDH1/2 mutation status were associated with their histology. Compared with the intermediate cell subtype of CHC-SC (CHCs-SC-int), CLCs were less frequently associated with chronic viral hepatitis, and showed lower levels of serum alpha-fetoprotein. Compared with iCCAs, CLCs showed lower levels of serum carbohydrate antigen 19-9 (CA19-9) and a lower frequency of expression of S100P. Patients with iCCA showed worse overall survival than those with CLC or CHC-SC-int. In patients with iCCA, CLC, or CHC-SC-int, a histology of iCCA, microvascular invasion, and serum CA19-9 value of >100 U/mL were significant poor prognostic factors for overall survival in univariate analysis. Multivariate analysis showed that a high serum CA19-9 value was an independent poor prognostic factor for overall survival.

CONCLUSIONS

Patients with CLC are likely to have a different etiology and mutational background from those with CHC-SC-int. Their clinicopathological manifestations are also different from those with classic iCCA. Our results suggest that CLC might be a distinct entity among primary liver carcinomas.