Abstract
PURPOSE: The active or aggressive character in certain localisations of aneurysmal bone cysts in children requires either curettage with a considerable recurrence rate or a radical segmental excision, raising complex reconstructive challenges. Cyst maturation with subsequent ossification may be observed either spontaneously or after incisional biopsy. PATIENTS: Five new cases of active aneurysmal bone cysts (ABCs) with healing of the cyst after biopsy alone are reported. All patients had no treatment of the cyst after the biopsy. RESULTS: In two cases, the lesion initially increases in size immediately after the biopsy, and it is only secondarily that the lesion decreases in size. Four out of five cases of the spontaneous healing occurred in pelvic bone. The cysts healed after, respectively, 36, 24, 12, 32 and 12 months. CONCLUSIONS: The emergence of these new cases of spontaneous healing encourages promoting clinical and radiological supervision after biopsy in selected cases. Unfortunately, it is impossible to predict a possible aggressive behaviour in ABCs. Then, if the lesion is quickly aggressive with clinically and radiologically increasing size after biopsy, it would be illogical and dangerous to let this ABC evolve. It would be necessary to treat it without delay. On the other hand, if the lesion moderately increased after the biopsy, it is possible to wait and observe the patient during a period of 5 months for a possible healing, if the ABC localisation is not dangerous. Of course, if the lesion does not increase in size after biopsy, there is no delay to treat it.