Rhabdomyosarcoma with Mixed Embryonal and Alveolar Features

**Semantic type:** Neoplastic Process

**Definition:** A rhabdomyosarcoma composed of embryonic and alveolar components. It is characterized by the presence of spindle cells with myoblastic differentiation, a myxoid stroma, and fibrous septa. These tumors were previously considered variants of alveolar rhabdomyosarcoma. The lack of PAX3-FOXO1 fusions in most of these tumors suggests that are biologically and clinically related to embryonal rhabdomyosarcoma.

**Synonyms:** - Mixed Alveolar Rhabdomyosarcoma - Mixed Type Alveolar Rhabdomyosarcoma