Primary hyperparathyroidism with multiple brown tumors

In April 2010, a 19-year-old soccer player presented with a 4-week history of pain after a tap against his right knee

Medical and family histories were unremarkable and no abnormalities were found on physical examination

A radiograph of the right knee showed osteolytic lesions in the distal femur and the head of the tibia

On magnetic resonance imaging, the epiphyseal lesions were visualized as cystic and nonsclerotic and extended to the articular surface of the distal femur and proximal tibia (Figure 1)

Soft tissue extension was suspected from the tibia

Laboratory test results showed normal blood cell count, renal function, and concentration of C-reactive protein

Aneurysmatic bone cysts were suspected and a biopsy was performed

Histopathological examination detected spindle cell infiltrates with hemorrhages, fragmented trabecular bone, and numerous osteoclastic giant cells proliferating at a rate of 10% suggesting an aggressive giant cell lesion

Since it was still not determined whether the lesions were malignant, flourodeoxyglucose F 18 positron emission tomography/computed tomography was performed and found additional lesions in the left distal femur and the left mandible

Biopsy of the mandible showed the same type of tissue as seen in the right femur and tibia