Conoccurence of extraskeletal osteosarcoma and undiagnosed Paget disease in a 49-year-old female

Extraskeletal osteosarcoma (ESOS) represents a rare soft tissue entity, accounting for ⁓1% of all soft tissue malignancies. It is generally considered to have an even worse prognosis than bone osteosarcoma, therefore detailed investigations and proper treatment are required. ESOSs arising in the subcutaneous tissue are even rarer than the ones positioned in deep tissues, and they are considered to have far better outcomes. We present a case of a 49-year-old patient diagnosed with subcutaneous ESOS and Paget disease of the bone, which is not typical for the patient's age, considering that Paget disease of the bone tends to affect a population above 50 years. The coexistence of these two entities in a single patient and all their features make this case unique, and to the best of our knowledge, this is the first case reported.