Children’s Oncology Group

A b s t r a c t Objectives: To examine whether the frequency of fusion-negative alveolar rhabdomyosarcoma (ARMSn) increased coincident with changes in the definition of alveolar histology. Methods: We re-reviewed alveolar rhabdomyosarcoma (ARMS) in the Children’s Oncology Group study D9803, comparing histopathology with fusion status. Results: Our review of 255 original ARMS cases (compared with a control group of 38 embryonal rhabdomyosarcomas [ERMS] cases) revealed that many had an ARMS-like densely cellular pattern with cytologic features and myogenin expression more typical of ERMS. Following re-review, 84 (33%