ObjectiveTo explore the clinical features and sum up the laws of the hepatic focal nodular hyperplasia (FNH) in its diagnosis and treatment. MethodsFNH was an uncommon benign hepatic tumor that often posed diagnostic dilemmas. We analyzed retrospectively the clinical, imaging of ultrasound, imaging of computed tomography (CT) and magnetic resonance images (MRI), and pathological materials of 21 patients with FNH proven by the pathological diagnosis during 5 years from April 1996 through April 2001 in two hospitals. ResultsThe diagnosis of FNH remained a challenge for clinicians and surgeons. Rate of correct diagnosis of FNH was low preoperatively (19.0%). The lesions of FNH were seen in males and females (m/f: 14/7). Only three female patients (3/7) had the history of taking oral contraceptive. Patients with FNH were largely young and middle age persons (81.0% under 50 years), discovered by accident (57.1%), without infection of the hepatitis B virus (95.2%) and with normal liver functions (100%) and serum AFP levels (100%). Color Doppler ultrasound showed blood vessels passing through the lesion (80.0%) and there was abundant in blood (66.7%). CT scan showed that the lesion had transient immediate enhancement in 60.0% of patients and had homogeneous signal in 60.0% after bolus injection. MR imaging demonstrated early vigorous enhancement (64.3%), homogenous signal (57.1%) and having central scar (35.7%) in the lesion. The demonstration of a central scar in the lesion was very helpful for the diagnosis of FNH. MRI was more helpful for the diagnosis of FNH using liver specific contrast agents: superparamagnetic iron oxide（SPIO）. All patients underwent focus resection (18 cases) or segmentectomy (2 cases), except one having no treatment. ConclusionFNH shows some typical clinical and imaging features. We could increase the rate of correct diagnosis by comprehensively analyzing the clinical and imaging materials. It is very important and necessary to determine a definite diagnosis of FNH, hepatic adenoma (HA) and primary liver cancer (PLC) preoperatively, because the HA and PLC must be surgically resected, FNH can only be followed up.