Aneurysmal bone cyst (a study of 127 cases, 72 with longterm follow up).

127 cases of aneurysmal bone cyst are analysed, seventy two of which were followed up from one to fifteen years after treatment. Statistics on sex, age, site and localisation are reported. Symptoms, radiographic features, histological appearances and differential diagnosis are discussed. In half the cases the cyst was clearly shown to be of subperiosteal origin. The aetiology is unknown, but the pathogenesis seems to consist of a haemorrhagic and hyperplastic (not neoplastic) process which is progressive but has a tendency to become stabilised on reaching a certain point of maturation. Local excision is indicated or, in cases where this is difficult to carry out, radiotherapy. Recurrences occurred in 12 per cent of the cases, always within one year after operation. All cases were eventually cured and there was no evidence of malignant transformation.