To determine the tumor type produced following concomitant Pten and Pax7 depletion, we first performed ultrastructural analysis and that revealed ASPcKOP7cKO tumor features were no longer consistent with skeletal muscle but with leiomyosarcoma (LMS), including elongated cellular shape, grooved nuclei, and prominent rough endoplasmic reticulum (Fig. 8a). Here, PAX7 is linked to leiomyosarcoma.