Objectives: To evaluate how sarcomatoid carcinomas (SCs) would be classified on magnetic resonance imaging (MRI) by using the Liver Imaging Reporting and Data System (LI-RADS) and to assess imaging features of SC compared with other hepatic malignancies.
Methods: We retrieved 184 patients with pathologically confirmed SC (n = 46), hepatocellular carcinoma (HCC, n = 92), and intrahepatic cholangiocarcinoma (iCCA, n = 46) diagnosed between January 2006 and December 2017. Two readers independently reviewed MRI according to LI-RADS v2017. Classification rate of SC, as probably or definitely malignant but not specific for HCC (LR-M), was calculated. LR-TIV (tumor in vein) was subclassified as either 5V or MV. MRI features were compared between SC, HCC, and iCCA and between SC of LR-M and non-LR-M categories.
Results: Chronic liver disease was present in 71.7% (33/46) of patients with SC, and LI-RADS was applied for these patients. SC was classified as LR-M in 24 (72.7%) of 33 patients at risk. SCs that had been classified as LR-4/5/5V were significantly smaller (median, 1.9 cm; range, 1.0-4.2 cm) than SCs classified as LR-M/MV (median, 4.3 cm; range, 1.3-20.6 cm) on independent t test (p = 0.012). SCs commonly showed MRI features similar to iCCAs than to HCCs. Targetoid appearance and capsular retraction were more frequent in iCCA than in SC (p ≤ 0.009) on Pearson's chi-squared test or Fisher's exact test.
Conclusion: Most SCs can be classified as LR-M on MRI, but small lesions may be indistinguishable from HCCs.
Key points: • Most sarcomatoid carcinomas (SCs) are classified as LR-M on MRI by using LI-RADS v2017. • SC showed various LR-M features similar to those of intrahepatic cholangiocarcinoma. • Size of LR-4/5/5V SC was significantly smaller than that of LR-M/MV SC.
Keywords: Cholangiocarcinoma; Hepatocellular carcinoma; Liver neoplasms; Magnetic resonance imaging.