Fluorescent in situ hybridization detection of HER-2/neu gene amplification in rhabdomyosarcoma

Embryonal rhabdomyosarcoma is the most common malignant soft-tissue tumor in childhood, comprising 45-50% of childhood sarcomas. Cytogenetic studies of this tumor are rare. In view of the paucity of cytogenetic data on this cancer and based on the finding of HER-2/neu gene amplification in a number of cancers that was detected mostly using the traditional technique of immunohistochemistry, we decided to conduct a pilot study to investigate whether HER-2/neu gene amplification in this tumor can be detected using the newer technique of fluorescent in situ hybridization (FISH). Archival tissues of rhabdomyosarcoma were retrieved and FISH using an HER-2/neu probe was undertaken on formalin-fixed paraffin-embedded tissue sections using a protocol optimized for our laboratory at Rhode Island Hospital. Out of 9 cases of rhabdomyosarcoma studied to date, 1 case clearly showed HER-2/neu gene amplification. Thus, FISH is a sensitive technique suitable for the detection of oncogene amplification and the delineation of tumor heterogeneity in this tumor. Future experiments utilizing additional specimens from our centers as well as from other laboratories will be needed to extend the finding in the present pilot study.