10-20% of soft tissue sarcomas cannot be accurately classified with histology and immunohistochemistry (IHC) and require further molecular investigation. We report an unclassified myoid neoplasm in a 5-year-old girl presenting with localized left heel swelling and impaired weight-bearing. Histology and IHC determined this as an undifferentiated sarcoma. Molecular work-up of this soft-tissue lesion demonstrated a novel SRF-MKL2 fusion as well as chromosomal copy number anomalies including 1p, 6q, 22 loss, and 1q gain. Pathologic and molecular features of this tumor fit best in the SRF-rearranged family of cellular myoid tumors. The patient remains disease-free 20 months after margin-negative resection.