Atypical tetrasomy 18 in a hepatoblastoma patient

Constitutive aneuploidy often underlies developmental defects, while copy-number alterations are recurrent somatic events in cancers. Rarely, mosaic aneuploidy links developmental defects and cancer development, yet its molecular basis remains elusive. We report the first cancer case in a tetrasomy 18 patient—a female who developed hepatoblastoma at age two and remains recurrence-free 24 months post-surgery and chemotherapy. Whole-genome sequencing and Fluorescent in situ hybridization (FISH) uncovered a complex rearrangement with eight breakpoints between 18p11.32 to 18q12.1, present in 10% of liver and blood cells. Haplotype analysis revealed a pre-zygotic origin, with mosaicism arising from early rescue by loss of the rearranged chromosome. Strikingly, all tumor cells retained this rearranged chromosome. Single-nucleus RNA-seq of liver and hepatoblastoma tissue traced the aneuploidy’s evolution during gametogenesis, organogenesis, and tumorigenesis. This study provides insights into mechanisms of aneuploidy-driven cancer, highlighting the interplay of mosaicism, developmental defects, and tumor evolution in a rare genetic syndrome.

• Type: Other
• Archiver: European Genome-phenome Archive (EGA)