A case report: pediatric rhabdomyosarcoma presenting with bone marrow metastasis.

BACKGROUND

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and adolescents, yet bone marrow metastasis is relatively rare. The clinical manifestations and bone marrow features of RMS with bone marrow metastasis are atypical, leading to frequent misdiagnosis as hematologic malignancies or other solid tumors at initial presentation, which consequently delays treatment initiation.

CASE PRESENTATION: An 11-year-old male patient presented with hemorrhagic rash and arthralgia as the initial symptoms. Early bone marrow cytology was suggestive of acute myeloid leukemia (AML). Further immunophenotyping could not rule out neuroblastoma (NB). Subsequent contrast-enhanced MRI, PET-CT scans, and pathological biopsy confirmed the diagnosis of alveolar rhabdomyosarcoma (ARMS).

CONCLUSION

This case highlights that RMS can initially present with bone marrow metastasis, mimicking hematologic malignancies. When primitive immature cells are observed in bone marrow aspirates, RMS should be considered in the differential diagnosis. A definitive diagnosis relies on a comprehensive approach including immunohistochemical markers, molecular genetic testing, and advanced imaging to identify the primary lesion.