Chondroblastoma of bone--not a " benign disease": clinico-pathologic observations on sixty cases

Chondroblastomas (CBL) account for less than 1% of all bone tumors. A 46 year review (1955-2000) of bone tumors yielded 60 cases of CBL. This paper reviews their histology, radiology, clinical presentation and emphasizes that this seemingly benign lesion is capable of aggressive behaviour. Histopathology slides and radiographs of sixty patients were studied and clinical details and follow-up were obtained. There were 44 males and 16 females, aged between 10 to 30 years. Long bones were involved in 81.4% of the cases, tibia being the commonest site. Symptoms comprised pain (60%), local swelling (25%) and joint symptoms (5%) or a combination of these. Radiologically, an oval sharply demarcated lytic lesion predominantly in the epiphysis was noted in 50% of the cases. On microscopy all lesions revealed chondroblasts having irregular grooved nuclei and osteoclasts with 80% of the tumors showing chondroid differentiation and calcification. Treatment comprised curetting (34 cases), wide excision (21 cases), radical excision (1 case) and was unknown in 4 cases. Follow-up ranging from 2 to 26 years was available in 83.3% of the patients; six (10%) had local recurrence (at 6 months, 8 months, 1 year, 2 years, 3 years and 5 years), two (3.3%) developed lung metastasis (synchronous in one and at 18 months in the other) and spontaneous malignant transformation occurred in one (1.4%) patient after 9 years; subsequent to three local recurrences. CBL, though seemingly benign, can behave in an aggressive manner. Since there are no reliable histological features to predict biologic behaviour, regular long term follow-up is recommended.