Hepatic sarcomatoid carcinoma: magnetic resonance imaging evaluation by using the liver imaging reporting and data system.

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.