Purpose or Case Report: Describe imaging features of pediatric focal nodular hyperplasia (pFNH) in a large cohort of children with clinical, radiological and surgical management with a significant follow up period. We aim to provide an algorithm to treat these patients using the evidence base we have created.
Methods & Materials: Imaging of 88 children with 110 pFNH lesions from 1977-2018 were evaluated by 2 radiologists for features such as size, number, echogenicity/density/intensity, presence of central scar and enhancement pattern. All patients referred from 1996 were assessed for symptoms, risk factors, initial management, follow up and outcome. Results were used to form management guidelines for future patients.
Results: 88 patients (68% female) with 110 lesions were analysed. 10 patients (11.4%) had multiple pFNH. Size ranged from 1 - 29cm. Ultrasound (US) imaging was available for 89 lesions, CT in 50 lesions and MRI of lesions. pFNH are iso-/hyperechoic on US in 82.8% (72/87) with arterial Doppler flow in 74% (37/50). Contrast US shows typical enhancement in 87.5% (7/8). On CT, pFNH are iso-/hypodense in 94.9% (37/39) pre-contrast with typical enhancement in 69.6% (32/46). On MRI, pFNH are iso-/hypointense on T1 in 86% (43/50), iso-/hyperintense on T2 in 88% (44/50), hyperintense on diffusion in 80.6% (25/31) and show typical enhancement in 68.1% (30/44).

50 patients were referred after 1996 and comprised our surgical follow up cohort: 74% females, mean age 8.9 years old with 46% symptomatic. Follow up was for a mean length of 5.2 years. Mean long axis diameter pFNH lesion at diagnosis was 5.9cm. 74% of patients had active radiological and clinical surveillance, whereas 26% had primary surgical resection. Of the patients undergoing surveillance only, 25 (67.5%) had lesional growth, 6 (16.2%) showed stability and 6 (16.2%) showed lesional decrease. 9 (24.3%) of the observed patients had eventual surgery. 92% of patients were asymptomatic at the end of follow-up with no significant difference in the surgical and observational groups.
Conclusions: pFNH is a rare tumour which compared to adults can be large, multiple, atypical on imaging and have a weaker predisposition for females. Given our clinical findings, we propose an evidence-based conservative approach to treatment consisting of first-line radiological and clinical surveillance. However, surgery can still be considered first or second-line for patients presenting with compressive abdominal symptoms, rapid growth of persistent symptoms.