SNP genotyping of a sclerosing rhabdomyosarcoma: reveals highly aneuploid profile and a specific MDM2/HMGA2 amplification.

Since the first description of sclerosing rhabdomyosarcoma in 2000, 19 pediatric cases have been reported in the literature. However, it is debated whether sclerosing rhabdomyosarcoma represents a specific rhabdomyosarcoma entity or a variant of embryonal or alveolar rhabdomyosarcoma. To date, 6 sclerosing rhabdomyosarcoma karyotypes and 1 sclerosing rhabdomyosarcoma comparative genomic hybridization profile have been reported. We present the first whole-genome tumoral genotyping of a sclerosing rhabdomyosarcoma by high-density single nucleotide polymorphism array. The single nucleotide polymorphism genotyping revealed a complex pattern including gains and losses of whole chromosomes and an amplification of the 12q13-15 region. Amplification of the 12q13-q15 region containing SAS, GLI, CDK4, and MDM2 has been observed in rhabdomyosarcoma. In the present case, the 2 amplified target genes were MDM2 and HMGA2, excluding CDK4. The identification of a specific MDM2-HGMA2 amplicon excluding CDK4 has only been described so far in well-differentiated and dedifferentiated liposarcoma. Further studies are needed to assess if this anomaly is a specific marker of sclerosing rhabdomyosarcoma.