Aneurysmal Bone Cyst: An Uncommon Secondary Event in Calcaneal Chondroblastoma.

Chondroblastoma is an uncommon benign bone tumour, involvement of epiphysis of long bones is typical. Chondroblastoma of the calcaneum is uncommon and its association with secondary aneurysmal bone cyst is even rarer. Only two cases of calcaneal chondroblastoma associated with secondary aneurysmal bone cyst have been reported till date. A 22-year-old male presented to the department of orthopaedics with complains of pain and swelling in the left heel since the last 10 months. On clinico-radiological grounds differentials considered were giant cell tumour of bone and aneurysmal bone cyst. In view of the histopathological findings of bone curettage and results of special stain and immunohistochemical marker, final diagnosis of chondroblastoma with secondary aneurysmal bone cyst, left calcaneum was rendered. Although rare, chondroblastoma should always be considered in osteolytic lesions of calcaneum. The identification of secondary aneurysmal bone cyst component is important as it has higher chances of recurrence than usual chondroblastoma.