MR findings of steatotic focal nodular hyperplasia and comparison with other fatty tumours

To correlate MR findings with pathology in steatotic FNHs and to compare the MR findings with those of other fatty tumours developed on noncirrhotic liver in a consecutive series of resected lesions. Our population included resected FNH with intralesional steatosis (n = 25) and other resected fatty tumours selected as controls (hepatocellular adenomas and angiomyolipomas, n = 34). Lesions were classified into three groups: those with typical FNH without (group 1) or with (group 2) fat on MR and those with atypical lesions (group 3). In group 3, diagnostic criteria for other fatty tumours were applied. There were 9 lesions in group 1 (15.3 %), 4 in group 2 (16.8 %) and 46 in group 3 (77.9 %). Group 3 contained 12 FNHs (26 %) and all the other fatty tumours. In group 3, the association of lesion homogeneity, signal intensity similar to or slightly different from adjacent liver on in-phase T1- and T2-weighted sequences, and strong arterial enhancement was observed in 7/12 (58 %) of steatotic FNHs and 3/34 (9 %) of other tumours. On MR, fat within a typical FNH should not reduce the diagnostic confidence. We recommend further investigations including liver biopsy if necessary when fatty tumours exhibit atypical MR findings. aEuro cent MRI is increasingly used to assess hepatic lesions containing fat. aEuro cent Nodules of focal nodular hyperplasia often contain foci of fat. aEuro cent However, steatotic FNH does not always demonstrate typical fatty features on MRI. aEuro cent The main mimickers of steatotic FNHs are telangiectatic/inflammatory hepatocellular adenomas. aEuro cent We recommend liver biopsy when fatty tumours exhibit atypical MR findings.