Outcomes of Patients Treated for Hepatoblastoma with Low Alpha-Fetoprotein and/or Small Cell Undifferentiated Histology: A Report from the Children’s Hepatic Tumors International Collaboration (CHIC)

SIMPLE SUMMARY: Hepatoblastoma is the most common malignant liver tumor in children. Small cell undifferentiated histology and low alpha-fetoprotein have been previously reported as factors associated with poor prognosis. It is important to exclude rhabdoid tumors (a rare pediatric liver tumor that is difficult to cure) in patients diagnosed with hepatoblastoma with alpha-fetoprotein levels less than 100 ng/mL and in patients with hepatoblastoma with small cell undifferentiated histology since the treatment for these patients is very different. When rhabdoid tumors are correctly diagnosed with testing for loss of SMARCB1, neither hepatoblastoma with small cell undifferentiated component nor alpha-fetoprotein less than 100 ng/mL confer poor prognosis. ABSTRACT: Small cell undifferentiated (SCU) histology and alpha-fetoprotein (AFP) levels below 100 ng/mL have been reported as poor prognostic factors in hepatoblastoma (HB); subsequent studies reported SMARCB1 mutations in some SCU HBs confirming the diagnosis of rhabdoid tumor. The Children’s Hepatic tumors International Collaboration (CHIC) database was queried for patients with HB who had AFP levels less than 100 ng/mL at diagnosis or were historically diagnosed as SCU HBs. Seventy-three of 1605 patients in the CHIC database were originally identified as SCU HB, HB with SCU component, or HB with low AFP levels. Upon retrospective review, they were re-classified as rhabdoid tumors (n = 11), HB with SCU component (n = 41), and HB with low AFP (n = 14). Seven were excluded for erroneously low AFP levels. Overall survival was 0% for patients with rhabdoid tumors, 76% for patients with HB with SCU component, and 64% for patients with HB with AFP less than 100 ng/mL. Patients with HB with SCU component or low AFP should be assessed for SMARCB1 mutations and, if confirmed, treated as rhabdoid tumors. When rhabdoid tumors are excluded, the presence of SCU component and low AFP at diagnosis were not associated with poor prognosis in patients diagnosed with HB.