Aggressive aneurysmal bone cyst of the maxilla confused with telangiectatic osteosarcoma.

Aneurysmal bone cyst (ABC) is a benign, expansile lesion typically affecting the long bones and vertebrae of patients younger than 20 years. Approximately 2% of ABCs occur in the head and neck region, most commonly affecting the mandible. Although the most common co-existing lesion associated with ABCs is the giant cell tumor, ABCs can be radiologically confused with telangiectatic osteosarcoma in cases of aggressive behavior and rapid growth. Here, we report a case of an aggressive ABC of the maxilla confused with telangiectatic osteosarcoma in a patient who underwent several operations for an osteoblastoma that was diagnosed histopathologically. This case highlights the need for a differential diagnosis both radiologically and histopathologically, because ABCs can easily be interpreted as a giant cell tumor or an osteoblastoma, and, on occasion, can be mistaken for osteogenic malignancies.