Uncommon localization of the Aneurysmal Bone Cyst

Aneurysmal bone cyst (ABC) is an expansile, osteoclastic, giant cell-rich bony neoplasm. It’s a rare benign tumor that accounts for only 1-2% of all primary bone tumors. ABC is typically eccentrically located in the metaphysis of long bones. Only a few cases of the primary Aneurysmal Bone Cyst have been described in the patella. We reported in this work a case of a 24-year-old male, who suffered from a continuous anterior knee pain. Lateral X-ray of the knee showed osteolytic patellar lesion, occupying almost the whole patella. Magnetic Resonance Imagery (MRI) showed a bone cyst of the patella, with fluid-fluid levels and cortical thinning, suggesting an Aneurysmal Bone Cyst. The surgical treatment consisted of patella trepanning, followed by a large curettage, the histological analysis of the curettage product confirmed the diagnosis.