Combined hepatocellular cholangiocarcinoma: LI-RADS v2017 categorisation for differential diagnosis and prognostication on gadoxetic acid-enhanced MR imaging

To investigate the performance of the Liver Imaging Reporting and Data System (LI-RADS) v2017 for combined hepatocellular cholangiocarcinoma (cHCC-CCA) in the differential diagnosis from hepatocellular carcinoma (HCC) and prediction of prognosis on gadoxetic acid-enhanced MRI (Gd-EOB-MRI). Patients at high risk of HCC with pathologically confirmed cHCC-CCAs (n = 70) and a matched control of HCCs (n = 70) who had undergone Gd-EOB-MRI were included. LI-RADS category was assigned for each lesion by two radiologists. Imaging features and surgical outcomes were compared between cHCC-CCAs of LR-M and LR-5/4 using the χ2 test or Fisher’s exact test. Recurrence-free survival (RFS) was estimated using Kaplan–Meier survival curves and compared using the log-rank test. cHCC-CCAs and HCCs were categorised as LR-M, LR-5/4 and LR-TIV in 61.4% (43/70), 37.1% (26/70) and 1.4% (1/70) and 10.0% (7/70), 88.6% (62/70) and 1.4% (1/70), respectively. cHCC-CCAs of LR-5/4, in comparison to LR-M, showed significantly higher frequencies of major HCC features: arterial hyperenhancement (96.2% (25/26) vs. 58.1% (25/43), p = 0.001), washout appearance (80.8% (21/26) vs. 48.8% (21/43), p = 0.011) and enhancing capsule (34.6% (9/26) vs. 11.6% (5/43), p = 0.031). After curative surgery, patients with cHCC-CCAs of LR-M showed a higher early recurrence rate (≤ 6 months) than did those with LR-5/4 (27.8% (10/36) vs. 4.8% (1/21), p = 0.041), whereas no significant difference was observed in RFS (log-rank p = 0.084). By using LI-RADS on Gd-EOB-MRI, a substantial proportion of cHCC-CCAs can be categorised as non-LR-M. In addition, cHCC-CCAs mimicking HCCs on imaging (LR-5/4) may indicate better surgical outcomes with regard to early recurrence than those of LR-M. • cHCC-CCAs can be categorised as either LR-M or non-LR-M on Gd-EOB-MRI. • cHCC-CCAs of LR-5/4 frequently demonstrate major HCC imaging features. • LI-RADS categorisation may provide prognostic information after surgery in cHCC-CCAs.