Myxofibrosarcoma is a rare cause of swelling in the upper extremities. The rarer form arising in the deep tissues can present a diagnostic difficulty. The treatment of high-grade myxofibrosarcoma in the extremity requires tissue diagnosis, accurate staging, careful multidisciplinary agreement on treatment, accurate execution of that treatment, and finally regular specialist surveillance. The treatment must be planned on an individual basis, weighing the risk of distant metastasis against the potential for severe functional impairment should radical excision or amputation be performed. The grade of tumor, clinical stage as well as the site, local extent, and the comorbidity of the patient influence the decision.We present the case of an elderly woman with an expanding high-grade myxofibrosarcoma within the thenar musculature of the nondominant hand. She presented with early signs of complex regional pain syndrome, leading to a treatment dilemma. We feel this case has important learning points on assessing objectives, risks, and outcomes in the management of these types of cases, and it highlights the role of multidisciplinary involvement in sarcoma management.