Primary osteosarcoma arising from subcutaneous tissue: 5-year follow-up.

Extraskeletal osteosarcomas are extremely rare, high-grade neoplasms. Approximately 300 cases have been reported in the literature, with a 5-year survival of around 25%-37%. Extraskeletal osteosarcomas frequently arise from lower-extremity, deep soft tissue planes, including hemorrhagic, necrotic areas. While primary osteosarcomas have been observed in the first two decades of life, osteosarcomas arising from the skeletal system are rarely observed before 40 years of age. We present radiological findings of an osteosarcoma case arising from cruris subcutaneous tissue in a young adult (31 years old) at diagnosis and at the follow-up period during a 5-year monitoring process. Additionally, we reviewed the literature regarding this case.