Aneurysmal bone cyst of the calcaneum: an expansile locally destructive lesion.

Aneurysmal bone cyst (ABC) is a benign but locally destructive lesion affection of which in the calcaneum has rarely been reported in the literature. We report an unusual case of ABC of the calcaneum in a 17-year-old-male, who presented with painful ankle swelling with difficulty in walking. Radiology revealed benign cystic calcaneal lesion, without any evidence of fracture. Biopsy was characterized by formation of osteoid along with the presence of ecstatic blood-filled channels, consistent with ABC. However, this being an uncommon site for ABC, histopathology needs to be used to differentiate it from other benign and malignant entities, and a definitive diagnosis warrants clinical and radiological correlation. Most of the ABCs require surgical curetting and bone engraftment of the surgical defect.