Nonspecificity of the fat-sparing ring surrounding focal liver lesion at MR imaging

RATIONALE AND OBJECTIVES: The presence of a fat-sparing ring surrounding focal liver lesions in patients with steatosis has been described only in malignant lesions. Our purpose is to evaluate whether this fat-sparing ring peripheral to tumors is a specific marker of malignancy. MATERIALS AND METHODS: From 300 magnetic resonance examinations of focal liver lesions, 132 patients with a confirmed nature of the lesions were selected. There were 24 patients (18.2%) with lesions having a perilesional fat-sparing ring in the opposed-phase spoiled T1-weighted gradient echo images. All these livers had steatosis. RESULTS: Perilesional fat-sparing rings were observed in 19 (21.6%) malignant and 5 (11.4%) benign lesions. Size of the lesion was not related to the presence of the fat-sparing ring (P=.6), neither was type of lesion (malignant versus benign) statistically related to the presence of the perilesional fat-sparing ring in the opposed-phase gradient echo magnetic resonance images (chi-square, P=.15). Fat-sparing rings were mainly seen in metastases (51.4% of metastases), but seldom in primary malignant tumors (1.9% of hepatocellular carcinomas). Hemangiomas also presented this finding (18.5% of hemangiomas). CONCLUSIONS: We believe that the presence of this bright rim surrounding lesions on oppose-phase images in patients with steatosis mainly represent decrease portal flow, either because of compressed and atrophic hepatocyte cords with sinusoidal congestion in expanding metastatic lesions or the presence of arterioportal perfusion abnormalities in vascularized hemangiomas.