Cytogenetic abnormalities in 42 rhabdomyosarcoma: A United Kingdom Cancer Cytogenetics Group Study

Background. Rhabdomyosarcomas are the most common type of pediatric soft ti ssue sarcoma. The cytogenetic literature on RMS is biased towards the less common alveolar subtype (ARMS), which is frequently associated with specifi c translocations and the PAX3/7-FKHR fusion genes. Relatively few karyotype s are reported for the embryonal subtype (ERMS). The aim of this study was to further cytogenetic knowledge of RMS subtypes. Procedure. Representative examples of all karyotypes from UKCCG member laboratories were reexamined and their histopathologies reviewed through the United Kingdom Children's C ancer Study Group (UKCCSG). Molecular evidence for the PAX3/7-FKHR fusion g enes was available for five ERMS and seven ARMS cases and compiled with the karyotypes. Results. Clonal chromosome aberrations were characterized for 25 ERMS and 17 ARMS cases. Thirty-six percent of the ERMS cases involved tr anslocation breakpoints in the 1p11-q11 region. Ten of the seventeen cases of ARMS showed cytogenetic evidence for the t(2;13)(q35;q14), consistent wi th molecular data available from four of these. Two further ARMS cases reve aled a PAX3-FKHR and a variant PAX7-FKHR fusion gene product that were not detected cytogenetically. Conclusions. Many of the karyotypes from both sub types were complex. The frequent involvement of the 1p11-1q11 region and ga in of chromosomes 2, 8, 12, and 13 in ERMS may be functionally significant. There was no evidence for involvement of the PAX3/7-FKHR genes in ERMS, an d cryptic involvement was found in some ARMS. There were no consistent chro mosomal rearrangements associated with apparently translocation negative AR MS cases. Med. Pediatr. Oncol. 36:259-267, 2001. (C) 2001 Wiley-Liss, Inc.