Mucinous intrahepatic cholangiocarcinoma: a distinct variant

Abstract

Mucinous variant of intrahepatic cholangiocarcinoma (iCC) is rare, and its clinicopathological features and prognosis are far less clear. Six patients who had iCCs with more than 50% of mucinous component and 79 conventional iCCs were included in the study. The mean size of mucinous and conventional iCCs was 6.2 cm and 6.0 cm, respectively. The majority of patients (83%) with mucinous iCC presented at T3 stage or above, compared to 28% of the conventional group (p < 0.01). Three patients with mucinous iCC (50%) died within 1 year. The average survival time of patients with mucinous iCCs was significantly reduced compared to that of conventional group (9 months vs 2 years; P < .001). Immunohistochemistry was performed on 6 mucinous and 12 conventional iCCs with matched age, sex and stage, which revealed positive immunoreactivity in MUC1 (83% vs 58%), MUC2 (33% vs 17%), MUC5AC (100% vs 42%), MUC6 (50% vs 0), CK7 (83% vs 83%), CK20 (0 vs 17%), and CDX2 (17% vs 0) in mucinous and conventional iCCs, respectively. Molecular studies showed one mucinous iCC with KRAS G12C mutation and no BRAF or IDH1/2 mutations. Mucinous iCC is a unique variant that constitutes 7.2% of iCCs. It is more immunoreactive for MUC1, MUC2, MUC5AC and MUC6. Unlike adenocarcinomas of colorectal primary, mucinous iCCs are often CK7+/CK20-/CDX2- and microsatellite stable. Patients with mucinous iCC likely present at advanced stage upon diagnosis with shorter survival time compared to the conventional counterparts.