[Aggressive aneurysmal bone cyst in childhood (author's transl)].

Case presentation of a four year old child with aggressive aneurysmal bone cyst of the fourth lumbar vertebra. Microscopic examination demonstrates a benign lesion. The roentgenographic pattern reflects a tumorlike bone destruction with signs of malignancy. Clinically, progression and invasion, similar to a semimalignant tumor, is noticed. The possible nature of this aggressive behaviour is discussed.