Purpose or Case Report: Focal nodular hyperplasia (FNH) is a benign lesion. Gadoxetate disodium (Eovist), a hepatocyte specific contrast agent, is becoming more widely used in pediatric MR imaging. FNH is composed of hepatocytes and should demonstrate homogeneous enhancement on the hepatobiliary phase of imaging; however, in clinical practice a variety of enhancement patterns have been observed. The purpose of this study is to document the features of FNH on hepatobiliary phase MRI in pediatric patients.
Methods & Materials: Institutional review board approval was obtained. Radiology records were searched for pediatric (<18 yrs) MRI examinations performed with gadoxetate disodium between 9/2010 and 9/2015 containing at least one the following terms: “focal nodular hyperplasia” or “FNH”. Clinical records were reviewed for the following: demographics; malignancy/chemotherapy; non-cancer related liver disease; liver surgery/biopsy. The most recent MRI was reviewed independently by 2 fellowship trained pediatric radiologists. Only the arterial phase and delayed hepatobiliary phase (20 minute) axial images were evaluated. For the largest (or only) lesion in each patient, the following was recorded based on the hepatobiliary phase images: lesion size, location and number; central scar; enhancement pattern. Descriptive statistics were used.
Results: 18 patients (12 girls) met inclusion criteria (mean age 13.7 yrs; range= 4-17). 7 patients had prior malignancy/chemotherapy; 3 had non-cancer related liver disease. 11 patients had solitary lesions; 7 patients had multiple lesions. 57% (4/7) of cancer patients and 100% (3/3) of liver disease patients had multiple lesions. Mean lesion size was as follows: all patients = 2.6 cm (range 0.9-11.8 cm); cancer patients = 2.2 cm; liver disease patients = 1.8 cm; sporadic = 3.3 cm. 22.2% (4/18) of lesions had a central scar. Hepatobiliary phase enhancement patterns for the largest lesion in each patient were as follows: 39% (7/18) heterogeneous; 33% (6/18) homogeneous; 28% (5/18) peripheral; 0% (0/18) central. Cancer patients most frequently had homogeneous enhancement (57%; 4/7); sporadic lesions most frequently had heterogeneous enhancement (50%; 4/8); liver disease patients were split between the observed enhancement patterns (1 each).
Conclusions: FNH has a variety of enhancement patterns on hepatobiliary phase Eovist MRI. Across all patients, the most common enhancement pattern was heterogeneous, although in cancer patients the majority of lesions enhanced homogeneously.