Qualitative and quantitative assessment of intratumoral fat using chemical-shift MRI for predicting histological grade of hepatocellular carcinoma

OBJECTIVES: To evaluate intratumoral fat in hepatocellular carcinoma (HCC) using both qualitative and quantitative approaches based on routine chemical-shift magnetic resonance imaging (MRI), and to investigate its potential value in predicting histological grade. METHODS: This retrospective study included 282 patients with pathologically confirmed HCC between January 2015 and November 2025. Tumors were classified into low-grade and high-grade groups according to the Edmondson-Steiner grade. Intratumoral fat was assessed on in-phase and opposed-phase MRI images. For qualitative assessment, intratumoral fat pattern was categorized as none, heterogeneous, or homogeneous. For quantitative assessment, regions of interest were manually delineated on three consecutive slices showing the largest tumor area, and the mean fat fraction (FF) was calculated. Logistic regression analysis was performed to identify risk factors associated with high-grade HCC. Furthermore, models incorporating clinicoradiological factors were developed for the preoperative prediction of HCC histological grade. RESULTS: Homogeneous intratumoral fat was more frequently observed in low-grade tumors than in high-grade tumors, and FF was significantly higher in low-grade tumors than in high-grade tumors. Both homogeneous intratumoral fat (odds ratio [OR] = 0.230 [0.097-0.514], P = 0.001) and FF (OR = 0.861 [0.811-0.907], P < 0.001) were identified as independent predictors of high-grade HCC. When combined with other clinicoradiological factors, the FF-based model showed better performance than the intratumoral fat pattern-based model (area under the receiver operating characteristic curve: 0.792 vs. 0.744, P = 0.024). CONCLUSION: Intratumoral fat assessed using chemical-shift imaging provides a simple and noninvasive imaging biomarker for predicting the histological grade of HCC. Both homogeneous intratumoral fat and higher FF were associated with a lower risk of high-grade HCC, and the model based on quantitative assessment outperformed that based on qualitative evaluation.