An aneurysmal bone cyst (ABC) is a benign bone tumor, but it has the potential to thin the bone and carries a high risk of recurrence. As with most tumors, the exact cause (etiology) of ABC is not fully understood.

This cyst is generally observed in individuals between 5 and 15 years of age and is most commonly found in the hip, shoulder, and knee regions of the body. Its incidence is higher in male children; this supports a hypothesis linking it to male children's higher activity levels and greater exposure to potential traumas.