Cytogenetics of hepatoblastoma: further characterization of 1q rearrangements by fluorescence in situ hybridization: an international collaborative study

BACKGROUND: Hepatoblastoma (HBT) is the most common hepatic neoplasm in children. This notwithstanding, little is known about pathogenetic factors, such as genetic abnormalities, of importance for the development and progression of this tumor type. To date, only 33 cytogenetically abnormal HBT have been published, and trisomies for chromosomes 2 and 20 have been shown to be the most frequent aberrations. Recently, unbalanced translocations involving proximal 1q have been described in several HBT, suggesting that a pathogenetically important gene maps to 1q. PROCEDURE: Six primary and one recurrent HBT were cytogenetically analyzed after short-term tissue culture. In addition, fluorescence in situ hybridization (FISH) studies, using locus-specific probes, were performed on three of these pediatric HBT as well as on one previously reported adult HBT. RESULTS: Total or partial trisomy 8, gain of chromosome 20, and structural rearrangements of chromosome 1 were detected in three HBT, and overrepresentation of chromosome 2 material was found in two HBT. The adjacent chromosome bands 1q12 and 1q21 were involved in three translocations, t(1;2), t(1;4), and t(1;11), which were all unbalanced and resulted in gain of 1q material. The previously reported adult HBT displayed 1q deletions with breakpoints at 1q12-21. FISH analyses of the 1q rearrangements revealed that all breakpoints were within the heterochromatic region. CONCLUSIONS: These findings provide further support for the importance of trisomies 2, 8, and 20 and rearrangements of 1q in the development of HBT. Furthermore, the consistent localization of breakpoints within the heterochromatic segment of chromosome 1 suggests that the important pathogenetic consequence of 1q abnormalities is the resulting genomic imbalance rather than a specific gene rearrangement.