Molecular cytogenetics of pediatric adipocytic tumors

Both epidemiologic and cytogenetic data on pediatric adipose tissue tumors are scarce. Pediatric adipose tumors are mainly represented by lipomas, though only 28 cytogenetic descriptions of pediatric lipoma have been reported to date. Similar to adult cases, most of these pediatric lipomas harbored rearrangements of the chromosomal regions 12q14-q15 and 6p21, involving the HMGA2 and HMGA1 genes. Further cytogenetic studies of pediatric lipoma would be useful to determinate whether some partner genes of HMGA2, such as NFIB, may have a specific role in the early onset of these tumors. Cytogenetically, the best documented pediatric adipose tumor is lipoblastoma, which is the second most frequent adipose tumor in children. Chromosomal alterations in lipoblastoma, observed in 61% of cases studied by conventional cytogenetics, typically involve the 8q11-q12 region. The target gene of this rearrangement is PLAG1. Anomalies of PLAG1 have been observed in 70% of cases of pediatric adipose tumors studied by molecular cytogenetics methods, such as fluorescence in situ hybridization (FISH) or comparative genomic hybridization on array (array-CGH). The rare described cases of malignant pediatric adipose tumors in children are mostly myxoid liposarcomas. In the 27 cases explored at the genetic level, all pediatric myxoid liposarcomas showed the classical rearrangement of the DDIT3 gene at 12q13. In conclusion, the epidemiology and the prevalence of histological types of adipose tissue tumors differ in the pediatric population compared with adults, whereas chromosomal and genic rearrangements are similar to those of adult cases in each histological type.