MYOD1 and soft tissue sarcoma: Our observation that MYOD1 mutations invariably co-occur with mutation in a second gene, most notably PIK3CA and CDKN2A, is consistent with a recent report.26 The co-occurrence with CDKN2A is of interest given that a recent large survey of soft tissue sarcomas of multiple histologies, including a small number of RMS tumors, implicated CDKN2A as a biomarker of poor prognosis.39 Although our study indicates that CDKN2A alterations may have prognostic value independent of MYOD1, this conclusion is based on low overall numbers.