Isolated Multiple Skeletal Muscle Metastases Detected By 123I-MIBG SPECT/CT in a Patient With Intermediate-Risk Neuroblastoma

A 3-year-old boy diagnosed with intermediate-risk neuroblastoma underwent routine follow-up using 123I-MIBG SPECT/CT imaging, which revealed abnormal radiotracer uptake at 2 distinct sites-located in the left vastus lateralis and right gastrocnemius muscles-highly suggestive of skeletal muscle metastases. The diagnosis was subsequently confirmed by histopathologic examination following biopsy. After 4 years of follow-up, a repeat 123I-MIBG SPECT/CT scan demonstrated no residual or new abnormal tracer accumulation, indicating a complete metabolic response. This case highlights that isolated multiple skeletal muscle metastases, although rare, can occur in patients with intermediate-risk neuroblastoma and may achieve sustained remission with appropriate management.