Giant Cell Tumor of Bone
Section snippets
Clinical history
GCT has a significant incidence, accounting for 20% of all benign bone tumors and 5% of all bone tumors, malignant and benign [6]. Higher incidence has been reported for the Chinese population, in which it can be up to 20% of all bone tumors [7]. Although some series show a slight female predominance [6], [8], [9], most support that there is no sex predilection in GCT. GCT of bone most frequently occurs in young adults between 20 and 40 years of age (Fig. 1) [6], [9], [10]. Occurrence before
Radiology
Radiographically, GCT of bone displays features that are somewhat characteristic and help in the establishment of a presumptive diagnosis. GCT is usually purely lytic and eccentric within the bone (Fig. 5). As previously stated, in long bones, it is found in the metaphyseoepiphyseal region. The tumor appearance is geographic, with ill-defined borders and often without any identifiable sclerosis. Cortical and cancellous bone likewise appear destroyed. Although aggressive appearing, a permeative
Staging
Although radiographic findings may suggest GCT of bone, as for any suspicious bone lesion, a full staging strategy is highly recommended. This strategy could include a CT scan or MRI of the affected area to evaluate the full local extent of the lesion, a total body bone scan to rule out additional asymptomatic bony lesions, and a chest radiograph to exclude lung involvement. Basic blood work can be obtained, although no specific abnormalities are expected. If hypercalcemia and or
Histology
GCT shows increased cellularity, with numerous multinucleated giant cells uniformly dispersed among a large population of mononuclear cells that are important for diagnosis (Fig. 8). There is little or no intercellular substrate other than a few collagen fibers. Mononuclear cells can be round, oval, polygonal, and sometimes spindled. They exhibit little cytoplasm. The nuclei contain one or more nucleoli and can exhibit variable amounts of hyperchromasia that is different from malignancy.
Basic sciences
There is evidence that three types of cells are found in benign GCT of bone [43]. Type I cells look like interstitial fibroblasts, make collagen, and have the capacity to proliferate. This cell population is likely the tumor component of GCT [43]. Type I cells share some features of mesenchymal stem cells from which they could be derived; however, they possess features that suggest they could represent an early differentiation of mesenchymal stem cells into osteoblasts [28], [44], [45], [46],
Treatment
GCT of bone is benign and most frequently involves the end of a long bone adjacent to a joint in a young adult. The best treatment should insure local control and maintain function. Curettage has been the preferred treatment for most cases of GCT. Historically, local recurrence rates of 25% to 50% have been reported (see Fig. 6, Fig. 8) [6], [7], [8], [13], [14], [16], [19], [61], [62], [63], [64]. The most recent series that have included modern imaging techniques and extended curettage
Function
Long-term functional results are usually very good after the treatment of GCT, even after curettage and grafting or cementing [66], [67]. Pathologic fracture through a GCT may be associated with persistent pain and lowered functional scores.
Lung metastasis from histologically benign giant cell tumor
Although it may seem odd to link lung metastases, a behavior usually associated with malignancy, to a benign bone process, it has been observed by many investigators [17], [77], [99], [100], [101], [102], [103], [104], [105], [106], [107]. The estimated incidence of this phenomenon is 3% [63]. On histology, the lung metastases are identical to benign GCT of bone. Increased incidence of lung metastases is associated with location of primary tumor in the distal radius or sacrum, stage 3 lesions,
Malignant giant cell tumors
Malignant GCT or giant cell sarcoma is rare [24], [111], [112], [113], [114], [115], [116]. Large series report an incidence of 5%. Spontaneous primary malignant GCT seems exceptional. Malignancy showing as a recurrence of a previously benign GCT is occasionally seen following curettage and without previous use of radiation (Fig. 10). The most often encountered scenario is a recurrent malignancy 1 to 10 years or more after irradiation of a previously benign GCT. A dosage as low as 40 Gy could
Follow-up
Due to the high incidence of local recurrence and the risk of lung metastasis, a close follow-up of patients who have GCT of bone is required. Follow-up appointments after treatment should be every 3 or 4 months and should include physical examination and plain radiographs of the involved bone. This follow-up allows for early detection of any recurrence. CT scan or MRI can be of great help when recurrence is suspected. It is unclear whether these imaging modalities have any role for routine
Summary
GCT of bone is a lesion with unpredictable behavior. It presents as a lytic defect in the end of long bone, most frequently affecting the knee area. Although benign, it is locally aggressive and deserves specific treatments that result in decreased local recurrence and preservation of function. Extended curettage followed by cement or bone grafting of some kind is the most often used treatment. En bloc resection is rarely a necessity and is used for more aggressive lesions when the bone or
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