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. The gene discussed is PIK3CA; the disease is soft tissue sarcoma.