Ancillary features in the Liver Imaging Reporting and Data System: how to improve diagnosis of hepatocellular carcinoma ≤ 3 cm on magnetic resonance imaging.

OBJECTIVES

To determine the strength of association with hepatocellular carcinoma (HCC) of each ancillary feature (AF) in LI-RADS version 2018, and to develop an appropriate strategy for applying AFs to improve the diagnosis of HCC ≤ 3 cm on gadoxetate-enhanced MRI.

METHODS

A total of 385 nodules (283 HCCs, 18 non-HCC malignancies, 84 benign nodules) of ≤ 3 cm in 266 patients at risk for HCC who underwent gadoxetate-enhanced MRI in 2016 were retrospectively evaluated. Two radiologists independently evaluated the presence/absence of AFs, and assigned a LI-RADS category to each nodule. Diagnostic odds ratio (DOR) of each AF was assessed. To improve the diagnostic performance for HCC, various criteria were developed based on the number of AFs favoring malignancy in general or HCC in particular. Generalized estimating equation models were used to compare the diagnostic performance of each criterion with that of the major features (MFs) only.

RESULT

All AFs favoring HCC in particular and malignancy in general were more common in the HCC group than in the non-HCC group. Of these AFs, hepatobiliary-phase hypointensity had the strongest association with HCC (DOR, 21.82; 95% confidence interval, 5.59-85.20). When we applied AFs in addition to MFs, the new criterion (with a number of AFs ≥ 4) had significantly higher sensitivity (80.6% vs. 70.0%; p < 0.001) than MFs only, without significant lower specificity (85.3% vs. 90.2%; p = 0.060).

CONCLUSIONS

The AFs varied in the strengths of association with HCC. More strict application of AFs (AFs ≥ 4) in LR-3 may improve the diagnostic performance for probable HCC ≤ 3 cm.

KEY POINTS

• The ancillary features (AFs) in the Liver Imaging Reporting and Data System version 2018 showed variable frequencies of occurrence and strengths of association with hepatocellular carcinoma (HCC). • Of the various AFs, hepatobiliary-phase hypointensity had the highest frequency and strongest association with HCC on gadoxetate disodium-enhanced MRI. • When applying AFs in addition to major features, a criterion of four or more AFs significantly increased the sensitivity for diagnosing HCC, without a significantly decreased specificity, especially in LR-3 observations.