Trisomy 8 in Embryonal Rhabdomyosarcoma Detected by Fluorescence In Situ Hybridization

Embryonal rhabdomyosarcoma is the most common malignant soft-tissue tumor in childhood. Cytogenetic studies of this tumor are rare. In one study trisomy 8 was found to be a primary cytogenetic abnormality. In view of the findings of trisomy 8 in a multitude of cancers, we conducted a pilot study to test the hypothesis that a subset of rhabdomyosarcoma also exists with trisomy 8. Accordingly, archival tissues of 12 cases of rhabdomyosarcoma were retrieved and fluorescence in situ hybridization (FISH) using a chromosome 8-specific, α-satellite probe was undertaken on formalin-fixed paraffin-embedded tissue sections using the protocol optimized in the Cytogenetics Laboratory at Rhode Island Hospital. The results obtained demonstrated that 6 of 12 tumors showed chromosome 8 trisomy, when a 15% threshold is adopted. In addition, one case was borderline, with 11% of the cells found positive for three fluorescent signals. Future experiments utilizing additional specimens from our centers as well as from other laboratories are needed to confirm and extend the findings of the present study.