Aneurysmal Bone Cyst : Clinical Features
Sites: Aneurysmal bone cysts (ABCs) usually involve metaphysis of long bones (femur, tibia, humerus), flat bones (pelvis, scapula) and the spine (15% of cases). The most frequent location is around the knee joint (distal femur and proximal tibia). The tumor originates in the medullary cavity and is located eccentrically (an important distinguishing radiographic feature from unicameral bone cyst). Some cases arise from the bone surface (cortex or periosteum). Occasionally, ABCs involve small bones of hands and feet (5% of cases). In spine, it can occur at any level (except the coccyx) and involves posterior elements (vertebral arches) but may encroach on the vertebral body. Sometimes, multiple vertebrae are involved. Rare cases with typical features of ABC are seen in soft tissues. Clinical Presentation: ABC is usually seen in children and young adults (75-80% of patients are between 10 and 20 yrs. of age) with no sex predilection. Patients present with pain/tenderness at the site, swelling and limitation of range of motion. Pathologic fracture is a rare complication. Tumors involving vertebrae can cause spinal cord compression and produce neurologic symptoms such as paresthesia and numbness in the extremities. Slide courtesy of Piero Picci, M.D., Director, Laboratory of Experimental Oncology, Instituto Ortopedico Rizzoli, Bologna, Italy. Used with permission.