[Differential diagnosis of giant cell-rich lesions of bone]

The diagnosis of giant cell-rich lesions of bone is often problematic even for the experienced pathologist. The diagnostic key lies in multinucleated osteoclast-like giant cells and a mononuclear stroma. From the histological picture alone it is often difficult to distinguish between individual entities such as conventional giant-cell tumor of bone, non-ossifying fibroma, giant-cell tumor in hyperparathyroidism or an aneurysmal bone cyst. Furthermore, these lesions can be confused with malignant bone tumors such as giant cell-rich osteosarcoma. X-ray is important for a correct diagnosis since some of these tumors show a typical anatomic location, while age of the patient is also an important factor. In most cases diagnosis is made on the basis of intraoperative frozen-section, but even in this setting, due to the poor quality of the material, it is very difficult to make a correct diagnosis of giant cell-rich lesions without X-ray and clinical data.