Atypical CT and MRI Features of Focal Nodular Hyperplasia of Liver: A Study with Radiologic-Pathologic Correlation

Abstract

Focal Nodular Hyperplasia (FNH) is the second most hepatic tumor next to hemangioma predominantly affecting women. It is a benign regenerative nodule having an unencapsulated well-defined mass with fibrovascular septae and proliferating bile ductules. Gadoxetic acid is a hepatocyte specific MR contrast agent which is known to be specific for the identifying FNH. Congenital vascular malformation and enlargement due to hormone stimulation is being considered as the main cause of FNH. The central stellate fibrovascular scar is a typical diagnostic imaging feature of FNH and the atypical pathological findings of FNH include large lesions multiple in number, internal necrosis, haemorrhagic foci and fatty infiltration. The atypical imaging features include non-enhancement of the central scar, calcification of the lesion, nonvisualized central scar and pseudocapsular enhancement on delayed imaging. For the accurate diagnosis of FNH, study of atypical radiologic features of FNH in correlation with pathological findings is the most essential. The macroscopic and the microscopic pathognomic changes should be taken as helpful points in the diagnosis of FNH. The main objective of this study is to recognize and understand the typical and atypical imaging patterns observed in CT and MR imaging of FNH with pathological correlation which avoids the necessity of biopsy and further investigations.