Epiphyseal chondroblastoma (a study of 39 cases).

A fully documented series of thirty nine cases of epiphyseal chondroblastoma is described. This is a remarkable series because of the rarity of this tumour. There is a slight predilection for the male sex. The age most affected is ten to twenty years. The tumour progresses slowly and joint involvement and pain are slight. The commonest site is the proximal epiphysis of the humerus, followed by the epiphyses of the knee. The classical appearances are of a clearly defined area of osteolysis, central or eccentric, with foci of calcification, in the epiphyseal or apophyseal regions, and often transgressing the epiphyseal cartilage. We have never observed involvement of the opposite bone in the affected joint. In four of our thirty nine cases the neoplasm invaded the point and/or soft tissues. The differential diagnosis, especially in localisations at the knee, is with giant cell tumour. The tumour is slow growing and the prognosis is always good. We have never seen malignant transformations or so-called "benign" pulmonary metastases. The few recurrences in this series (five out of thirty nine) were all cured by a second operation. Curettage and grafting is the operation of choice.