Giant Cell Tumor of the Patella: An Uncommon Cause of Anterior Knee Pain

The patella is a rare site for the development of primary tumors. This is the case report of a giant cell tumor (GCT) occurring in the patella in a 25-year-old woman. The patient presented with a 1-year history of occasional right anterior knee pain. The radiological characteristics suggested a benign condition. The intraoperative pathological diagnosis was GCT of the bone. The lesion was treated by radical curettage with adjuvant therapy comprising phenol and ethanol and injection of calcium phosphate cement. Histologically, the tumor consisted of round or spindle-shaped mononuclear cells admixed with numerous osteoclastic giant cells. The patient was asymptomatic and there was no evidence of local recurrence or distant metastasis 16 months after surgery. Although rare, patellar GCT may be included in the differential diagnosis of anterior knee pain and/or swelling, particularly in young adults.