Analysis of RNA sequencing data previously produced in our laboratory [35] identified the presence of both circular and linear AFF1 isoforms in human primary myoblasts, which are considered our non-transformed control, as well as in RD and RH4 cell lines, representative of embryonal rhabdomyosarcoma (ERMS) and alveolar rhabdomyosarcoma (ARMS), respectively. This evidence concerns the gene AFF1 and alveolar rhabdomyosarcoma.