Q: My 7-year-old son had an aneurysmal bone tumour removed from his proximal femur. The tumour was removed by curettage and allograft bone chips were used to fill the cavity. What is the possibility of recurrence?

A:An aneurysmal bone cyst is an expansile cystic lesion that may occur in any bone in the body. Although benign, it can be locally aggressive and cause extensive weakening of the bony structure and impinge on surrounding tissues. The true cause and pathophysiology remain unknown. The mainstay of treatment is intralesional curettage; however, recurrence is not uncommon. The prognosis for an aneurysmal bone cyst is generally excellent, although some patients need repeat treatments because of recurrence. A younger age, open growth plates, a metaphyseal location, stage 3 lesions have all been associated with an increased risk of recurrence. Morphologic types I and II recur more often than types III, IV, and V.