Aneurysmatische Knochenzyste (AKZ)

Summary Aneurysmal bone cyst (ABC) Aneurysmal bone cyst is a benign, destructive and aggressive lesion of the long bones, spine and pelvis, occurring mainly in children and young adults. The clinical signs, pain and quick-growing mass, are associated with radiological signs of an aggressive lesion. This suggests malignancy, but in typical cases it is really a totally benign lesion sometimes associated with genuine tumours such as chondroblastoma, osteoblastoma and (very rarely) osteosarcoma. The X-ray findings are usually typical; MRI bears out the clinical impression, but in most cases biopsy is necessary to confirm the diagnosis. Biopsy should be done with the utmost caution, due to the risk of cataclysmic bleeding. Treatment consists of curettage and bone grafting, but recurrences are frequent. Curettage associated with high-speed mechanical burr, cementation or phenol application may lessen the risk of recurrence. In selected cases broad resection can be done, provided there is no functional loss (e.g. peroneal nerve). After a resection of this kind the risk of recurrence is almost non-existent. This aggressive but benign lesion is rare and requires treatment by a specialist.