Most GCTs are present in the epiphyseal or epimetaphyseal end of the long bones.
If the epiphysis is not involved, a diagnosis of GCT is dubious. The radiographic findings are helpful but cannot clinch the diagnosis. Histological examination is still the gold standard for diagnosis.
To distinguish metaphyseal and diaphyseal GCT from other lesions is a challenge for the pathologist. Several lesions like aneurysmal bone cyst, giant cell-rich osteosarcoma, fibrous cortical defect, solitary (unicameral) bone cyst, and giant cell lesion of hyperparathyroidism (brown tumour) are more common in these sites than are true GCT. This extensive range of lesions with the exception of giant cell lesion of hyperparathyroidism, usually appears in the first two decades of life.
Aneurysmal bone cyst is clinically benign It commonly appears in the metaphysis. It contains prominent blood-filled spaces. The more solid zones within them exhibit fibrogenesis and osteoid trabeculae[12
]. The stroma between the spaces contains hemosiderin laden macrophages, chronic inflammatory cells and broad seams of reactive osteoid[5
]. Multinucleated giant cells are often conspicuous. Mitoses may be numerous, but anaplasia is absent.
Osteosarcoma is a lesion in the metaphysis and contains numerous benign giant cells. The stroma reveals cells with ananplasia and irregular size and shape. Also presence of cartilage is not uncommon[12
Fibrous cortical defect is a benign lesion which regresses spontaneously. Radiology shows a characteristic eccentric zone of rarefaction with well-defined scalloped margins[12
]. The microscopic picture reveals a mixture of collagen and fibroblasts with irregular cluster of histiocytes filled with lipid and hemosiderin. Multinucleated giant cells may be found[5
A simple bone cyst generally touches the epiphyseal growth plate. It is benign lesion and shows radiolucence with fine trabeculation. It contains fibrous tissue with few giant cells[12
A giant cell lesion of hyperparathyroidism appears in the metaphysis. Many giant cells scattered in a fibrogenic stroma may be present. A serum hypercalcemia and hypophosphatemia is characteristic[12
Giant-cell reparative granulomas demonstrate an appearance which suggests previous injury and inflammation with subsequent fibrosis. These lesions characteristically have an appearance which suggests previous injury and inflammation with subsequent fibrosis. Giant cells are found in the vicinity of old areas of hemorrhage, though not dispersed throughout the lesion. Mandible is a common site for these lesions[10
The case we have reported did not contain areas of hemorrhage, hemosiderin pigment, osteoid, bone, or significant amounts of collagen. The lesion also did not have the fibrotic, scarred appearance of a fibrous cortical defect, reparative granuloma, or brown tumor of hyperthyroidism. The patient had no detectable parathyroid dysfunction. The clinical and histological features of other osseous lesions which may contain giant cells were not present.
The patient's age, the location of the lesion, its roentgenographic appearance, and the gross and microscopic appearances are crucial to unravel the mystery of an osseus lesion. However, the final diagnosis depends on the tumour's histological appearance only[10
]. As Jaffe has mentioned 'A bone lesion may be uncharacteristic in all other respects, but if it exhibits the cytological pattern of a giant cell tumour, it should be recognised as a GCT' [18