The evolution of aneurysmal bone cyst

Abstract

The rare opportunity arose to observe an aneurysmal bone cyst first from a biopsy and then one year later in the resected specimen. The differing appearances of these two and the growing belief that this condition represents a dynamic process, prompted a review of the 6 cases filed at the Adelaide Children's Hospital over the years 1964-1971. Their histological features are used as criteria for classifying them into stages by means of which they are 'plotted' on an evolutionary 'graph'. The pattern which emerges appears to indicate that the aneurysmal bone cyst starts as a densely cellular lesion (histologically resembling giantcell tumour of bone), passes through a fibro-osseous phase in which fibrous tissue becomes predominant, sinusoidal blood vessels become prominent (and where there may be some resemblance to fibrous dysplasia), and finishes its evolutionary development as the familiar, typical, honeycombed, predominantly vascular lesion of the fully developed aneurysmal bone cyst. It is important to recognize the evolutionary nature of this benign lesion so that needless surgery may be avoided, but that action may be taken before it 'grows' to such a size that a mutilating procedure is inevitable.