BACKGROUND: Hepatoblastoma (HB) requires surgical resection for cure, but only 20-30% of patients have resectable disease at diagnosis. Patients who undergo partial hepatectomy at diagnosis have historically received 4-6 cycles of adjuvant chemotherapy; however, those with 100% well-differentiated fetal histology (WDF) have been observed to have excellent outcomes when treated with surgery alone. PATIENTS AND METHODS: Patients on the Childrens Oncology Group non randomized, multicenter phase III study, AHEP0731, were stratified based on Evans stage, tumor histology, and serum alpha-fetoprotein level at diagnosis. Patients were eligible for the very low risk stratum of surgery and observation if they had a complete resection at diagnosis and rapid central histologic review demonstrated HB with 100% WDF histology. RESULTS: A total of 8 eligible patients were enrolled on study between September 14, 2009 and May 28, 2014. Outcome current to 06/30/2020 was used in this analysis. The median age at enrollment was 22.5 months (range: 8-84 months) and the median AFP at enrollment was 714 ng/ml (range: 18-77,747 ng/mL). With a median follow-up of 6.6 years (range: 3.6-9.8 years), the 5-year event-free (EFS) and overall survival (OS) were both 100%. CONCLUSION: This report supports that HB with 100% WDF histology completely resected at diagnosis is curable with surgery only. The development of evidence-based surgical guidelines utilizing criteria based on PRETEXT group, vascular involvement (annotation factors), tumor-specific histology and corresponding biology will be crucial for optimizing which patients are candidates for resection at diagnosis followed by observation. LEVEL OF EVIDENCE: Prognosis study, Level I evidence.