Alveolar rhabdomyosarcoma with multiple bone marrow metastases: a case report.

Rhabdomyosarcoma (RMS) is rare but is the most common soft tissue sarcoma in children and teenagers. Alveolar rhabdomyosarcoma (ARMS), a subtype of RMS, primarily affects teenagers aged between 10 and 25 years old and is associated with early lymphatic and hematogenous metastases. This case report describes a 13-year-old girl with ARMS in the right thigh, accompanied by multiple bone and bone marrow metastases. Contrast-enhanced CT/MRI revealed a mass with marked heterogeneous enhancement and an enhancing pseudocapsule, while pathological examination confirmed the diagnosis through immunohistochemical markers (MyoD1 (+), Myogenin (+), Desmin (+)). This case highlights the aggressive nature of ARMS and the importance of characteristic imaging findings.