Giant cell tumours (GCTs) account for approximately 5% of all primary bone lesions. GCTs are benign and locally aggressive. These are usually solitary and are found most commonly at the DISTAL FEMUR or PROXIMAL TIBIA.
Pathology
The characteristic feature of GCTs is the presence of many OSTEOCLAST-LIKE GIANT CELLS typically with 40 to 60 nuclei per cell, in a matrix of mononuclear stromal cells. Hence the GCT is also called OSTEOCLASTOMA. The mononuclear stromal cells are the neoplastic cells not the osteoclasts.
Giant cells can also be seen in other conditions, such as aneurysmal bone cysts, fractures, and chondroblastomas. Therefore, the presence of giant cells under the microscope, does not mean that the patient has a giant cell tumour. Secondary aneurysmal bone cysts also may be present within these tumours. Tumour cells do not synthesize bone or cartilage. The tumour stroma is highly vascular.
The DIFFERENTIAL DIAGNOSIS should include other epiphyseal tumours such as chondroblastoma, brown tumour or hyperparathyroidism and, in the sacrum, chordoma.
Clinical features
These are most common between 20 and 45 years of age that is AFTER THE PHYSES HAVE CLOSED. GCTs typically affect the EPIPHYSIS of long bones of the DISTAL FEMUR, PROXIMAL, TIBIA, DISTAL RADIUS and PROXIMAL HUMERUS around joints. In the spine they most commonly arise in the vertebral bodies of the SACRUM.
Malignant transformation and metastasis can occur rarely in less than 5% cases. Secondary malignant giant cell tumours are sarcomas. These originate at the sites of previous tumours that have been treated, particularly with radiation.
Patients typically present with pain and, an increasing mass, usually around the knee. In 5–10% of cases, pathological fracture is the presenting feature.
Radiographic diagnosis
On plain radiograph GCTs are seen as classical eccentric, often subchondral, expansile, and loculated lytic lesions having ‘SOAP-BUBBLE’ APPEARANCE. Cortex may be thinned out or perforated at places. GCTs do not have matrix calcification, new bone formation or periosteal reaction.
Classification
Giant cell tumour (GCT) is a Tumour of Unknown Origin. GCTs are staged according to the CAMPANACCI CLASSIFICATION SYSTEM.
Treatment
These lesions are frequently treated satisfactorily with intralesional EXTENDED CURETTAGE followed by bone grafting or cement packaging . Very aggressive lesions require marginal or en-block resection.
BISPHOSPHONATES have been used as a surgical adjuvant or as an option in unresectable tumours. Chemotherapy has limited success, and radiotherapy should be reserved for symptomatic inoperable lesions such as those in the vertebrae.
Recurrence is a serious concern.
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