Structures that constitute soft tissue are muscle, tendon, nerve, blood vessel and fibrous tissues like fascia, capsule and ligament, fat, and synovium (Fig. 19.1). World Health Organization (WHO) subsumes these structures as “connective, subcutaneous, and other non-parenchymatous-organ soft tissues, as well as the peripheral and autonomic nervous system”. Tumors arising from these soft tissue structures are rare in children [1]. Most of the musculoskeletal soft tissue mass lesions in children are tumor mimic lesions such as ganglion cysts, vascular malformations, and benign lesions. Soft tissue sarcomas (STS) comprise only approximately 6% of all childhood malignant tumors, and rhabdomyosarcoma (RMS) is the most common STS in children [2, 3].