Malignant transformation of an aneurysmal bone cyst of the femoral neck: A case report.

Aneurysmal bone cyst (ABC) is a benign, distending, osteolytic and locally aggressive bone tumor that is mostly associated with trauma. Approximately 1% of bone tumors are ABCs, which are most prevalent in adolescents and are usually detected in the spine and long tubular bones. The diagnosis of ABC mainly relies on histopathology, malignant transformation is rare, and the chance of malignancy increases if there are multiple recurrences. Due to the rarity of reports of malignant transformation of ABCs into osteosarcoma, there is still considerable debate on the appropriate treatment strategy. The current paper presents a case of aneurysmal bone cyst malignant to osteosarcoma and the therapeutic measures to provide expertise for the diagnosis and treatment of ABCs that are malignant to osteosarcoma.