Embryonal Rhabdomyosarcoma : Molecular Genetics
Molecular & Cytogenetics of Embryonal Rhabdomyosarcoma (RMS): Many cases show complex cytogenetic findings consisting of chromosome gains and losses. One of the characteristic findings is LOH for multiple linked loci at 11p15.5 which results in inactivation of growth factors and tumor suppressor genes, including GOK, H19, CDKN1C, HOTS, and IGF2. Most cases show alterations of receptor tyrosine kinase/RAS/PIK3CA pathway. Alterations of the ALK gene are seen in both embryonal as well as alveolar RMS and correlate with metastatic disease and poor outcome. Trisomy 8 has been reported in embryonal RMS as well as upregulation of GLI1 and PTCH1 both of which are involved in the hedgehog pathway. The image shows paratesticular embryonal RMS in a young male. There are scattered primitive-appearing hyperchromatic tumor cells adjacent to epididymal tubules.