E1589. Evaluation of Hepatic Adenoma and Focal Nodular Hyperplasia With Atypical Features on MRI With Liver-Specific Contrast and Clinical Followup
  1. Roy Dwarkasing; Erasmus MC
  2. Paul van Westerveld; Erasmus MC
  3. Razvan Miclea; Erasmus MC
  4. Bibiche Gest; Erasmus MC
  5. François Willemssen ; Erasmus MC
Hepatocellular adenoma (HCA) and focal nodular hyperplasia (FNH) can be diagnosed with confidence on MRI with liver-specific contrast (gadobenate dimeglumine or gadoxetate disodium) (CE-MRI). Diagnosis may be problematic in case of atypical findings. The aim of this study was to investigate presumed HCA and FNH with atypical findings on CE-MRI.

Materials and Methods:
Between June 2008 and December 2019, 708 patients underwent CE-MRI of the liver in a tertiary referral center with presumed HCA or FNH. Clinical and radiological reports were reviewed in search of atypical findings with questionable diagnosis and histopathology (PATH) proven lesions. Included cases were reviewed (separate and blinded) by two radiologists with 2 and 15 years of experience respectively.

From a total of 158 patients with PATH proven lesions, 98 patients with typical unequivocal HCA or FNH were excluded leaving 60 (38%) patients (all women, mean age 42 years) with 62 lesions to be included. Indications for PATH were subcategorized: A) Malignancy could not be excluded (n = 37): 24 (64%) HCA, 7 (19%) FNH, 3 (8%) hepatocellular carcinoma (HCC), 1 cholangiocarcinoma (CCC), 1 focal fibrosis and 1 sclerosing hemangioma. B) Could not differentiate HCA from FNH (n = 14): 6 (43%) HCA, 4 (29%) FNH, 1 FNH/HCA mixed lesion, 1 regenerative nodule, 1 HCC and 1 CCC. C) Confident HCA or FNH but painful lesion (n = 6): 3 (49%) HCA, 1 HCA with HCC, 1 focal fibrosis and 1 benign possibly HCA. D) Confident HCA or FNH but lesion growth in follow up (n = 5, 8%): 4 (80%) HCA, 1 FNH. Interobserver agreement for classifying benign versus possible malignant lesion was good (kappa = 0.76, 95% CI 0.56 – 0.94). Overall, malignancy was found in 11% of atypical lesions on CE-MRI. In the total study cohort follow-up data revealed no missed malignancy.

In a large study cohort 62 of 708 (9%) patients with presumed HCA and FNH had atypical findings on CE-MRI of which 11% proved malignant. There were no missed malignant lesions. CE-MRI is an excellent modality for diagnosis of HCA or FNH, including depiction of lesions that resemble and proved malignancy.