Rhabdomyosarcomas (RMS) are one of the most common types of sarcomas in children and adolescents. The alveolar RMS subgroup is of particular interest because in some cases, the translocation of the PAX3 and FOXO1 genes is combined with an amplification of the corresponding hybrid gene. According to literature data, the frequency of the PAX3::FOXO1 translocation is 70—90% and the PAX7::FOXO1 translocation 10—30%.

OBJECTIVE

To determine the frequency of variable FOXO1 translocations in the alveolar RMS patient group.

MATERIAL AND METHODS

Thirty-two tumor samples were collected and analyzed using a combination of histological, immunohistochemistry (Myogenin, MyoD1), and molecular genetic techniques (fluorescence in situ hybridization (FISH) and real-time polymerase chain reaction (RT-PCR)).

RESULTS

Cytogenetic analysis using the FISH technique with a FOXO1-specific probe identified 26 (81%) samples with rearrangements at the FOXO1 locus and seven (19%) without rearrangements. Real-time PCR identified the translocation partners PAX3 in 58% (15/26) and PAX7 in 42% (11/26) of samples.

CONCLUSION

Four cytogenetic patterns were observed: classical translocation, translocation with amplification, translocation with deletion, and normal signal distribution. Alveolar rhabdomyosarcomas exhibit genetic heterogeneity and a diversity of cytogenetic profiles. The frequency ratio of PAX3/PAX7::FOXO1 variable transcripts is 1:1. Approximately 20% of cases of alveolar RMS do not have cytogenetic signs of rearrangements of the FOXO1 gene.