Synovial sarcoma is a well-defined soft tissue neoplasm often seated in a deep extra-articular extremity location, and it can be seen in both the pediatric and adult populations. Most lesions are firmly attached to adjacent structures. The indolent behavior and well-circumscribed appearance are commonly misleading toward a benign clinical diagnosis. In most cases, the preoperative duration of symptoms ranges from 2 to 4 years. Adequate surgical excision is the primary treatment modality, while radiotherapy is an essential adjunct for improved local control. In this chapter, we present the case of a 13-year-old male patient with synovial sarcoma of the forearm, which had been radiologically followed up for years before presentation to our clinic, with the presumed diagnosis of a soft tissue hemangioma. The lesion involving the proximal ulna presented a significant challenge in terms of both an oncologically safe resection and achieving the best functional outcome.