Giant cell tumor of bone is a benign, rarely malignant neoplasm consisting of mononuclear and giant multinucleated cells resembling osteoclasts. It is more often localized in the metaphysics of long tubular bones. It proceeds asymptomatically or is manifested by pain, swelling, local hyperthermia, restriction of movements. Diagnostics is based on survey data, objective examination, radiography, computed tomography, other hardware techniques, cytological and histological examination. Treatment – surgical intervention, radiation therapy.
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Giant cell tumor of bone (GCTB, osteoblastoclastoma, osteoclastoma) is a neoplasia with two clinical variants of the course. Data on the prevalence vary significantly – from 4 to 25% of the total number of tumor lesions of the skeleton. The proportion of the malignant variant is 5-10%. 80% of patients are in the age category of 20-50 years, the peak incidence occurs in the third decade of life. Women suffer slightly more often than men. In 50-65% of cases, the knee joint area is affected (distal part of the thigh or proximal part of the lower leg).
The etiology of giant cell tumors has not been definitively clarified. Specialists adhere to Peterson’s concept, common to all neoplasms, according to which neoplasia is a polyethological disease that occurs when external and internal adverse influences are combined. Exogenous risk factors include harmful biological (viral), chemical, and radiation effects. Endogenous factors are considered metabolic disorders, hormonal balance disorders, decreased reactivity of the body.
In 89%, GCTB is formed in long tubular bones. The lower extremities are affected two more often than the upper ones. The distal metaphysis of the femur occupies the first place in terms of prevalence, the second is the proximal part of the tibia or fibula, the third is the peripheral parts of the ray, the fourth is the distal part of the tibia. Vertebrae, small and flat bones rarely suffer.
Single foci are characteristic, separate double localizations are also described in the literature, often located close to each other in articulating bones. Giant cell tumor of bone is located in the metaphysis, sometimes growing towards the diaphysis. The primary diaphyseal location is extremely rare. Mononuclear neoplasm cells have similarities with osteoblasts, giant multinucleated ones – with osteoclasts. Bone beams and osteoid inclusions are detected in the neoplasia tissue.
Benign tumors have a typical structure. In case of malignancy, three options are possible. The first is that osteoclastoma metastasizes, preserving the standard structure (which is detected, including in remote foci). The second is the primary malignant GCTB, which differs from the benign one by the presence of atypia and mitosis mainly in single–core cells. The third is the transformation of primary benign osteoblastoclastoma into various types of sarcomas: osteogenic, fusiform cell, fibrosarcoma.
In most patients at the initial stage, the only manifestation of a benign (typical) giant cell tumor is pain in the affected area. Sometimes there is a connection between the pain syndrome and the previous traumatic injury. The symptom is expressed moderately, occasionally bothers with movements, has a nagging or dragging character. Less often, soreness is accompanied by the appearance of a tumor-like formation, even less often, swelling occurs without pain.
In adults, GCTB rarely manifests a pathological fracture. At the same time, the proportion of this trait in children is more than 50%. All manifestations, except for a pathological fracture, do not cause much concern, therefore, patients first consult a doctor 8 months or more after the onset of the disease, at the stage of formation of a detailed clinical picture. At this stage, pain is detected in all patients, increases with physical exertion, remains at rest, often worries constantly, increases at night.
Palpable neoplasia is found in 70-75% of cases. The remaining patients have local edema of soft tissues. A frequent symptom in this period is the restriction of mobility in the nearby joint. The manifestation is usually associated with increased pain during movements. Sometimes there are gradually forming contractures that are not directly related to the pain syndrome. In some patients, effusion is determined.
Malignant Giant cell tumor of bone is manifested by similar signs. The main differences are considered to be the insignificant duration of the period of primary symptoms, rapid progression, higher intensity of painful sensations. The neoplasm, on average, begins to be felt after 4 months, the detailed clinical picture is revealed six months after the appearance of the first symptoms of osteoblastoclastoma. Metastases to the lungs, other bones, and soft tissues are rarely detected.
Primary diagnostic measures are carried out by traumatologists-orthopedists, in the future patients are referred to specialists in the field of osteooncology. The nature of the pathology is determined on the basis of complaints, physical examination data, additional studies. During an external examination, a tumor-like formation of bone density, edema and hyperemia are detected, and the volume of movements is assessed. To clarify the type of neoplasm , the following methods are used:
- Bone x-ray. The images visualize cystic changes or neoplasia in the form of “soap bubbles” in the metaphysical zone. There are no signs of general osteoporosis, osteosclerosis can be seen around the altered area. The boundaries of benign GCTB are clearer, but due to locally aggressive growth with a significant size, the appearance of a “bone visor” is possible. Pronounced periosteal reaction is uncharacteristic. Malignant osteoclastoma has an indistinct structure. The images show early destruction of the cortical layer.
- CT and MRI of the bone. Computed tomography gives a clearer idea of the shape, size, and boundaries of a giant cell tumor, and in doubtful cases allows you to confirm or refute the rupture of the cortical layer. During magnetic resonance imaging, the intramedullary and cystic components are examined, the condition of the surrounding soft tissues, the location of blood vessels and nerves are assessed. The methods help to choose the best option of surgical intervention, plan the operation.
- Other hardware studies. In case of a malignant process, skeletal scintigraphy or PET-CT is prescribed. Due to the accumulation of osteotropic pharmaceuticals, the methods visualize the neoplasm well, identify secondary bone foci. Angiography in malignant course indicates the formation of a disordered vascular network with arteries of uneven diameter. Lung x-ray is indicated for suspected metastasis.
- Morphological studies. Verification of a giant cell tumor is carried out by cytological or histological analysis. The material is obtained by aspiration biopsy or trepanobiopsy. The probability of accurately determining the type and degree of differentiation of neoplasia is 80-90%, difficulties often arise with relapses. If there is insufficient information, repeated tissue sampling is performed by open biopsy.
- Other laboratory tests. The test results are non-specific, but contribute to the differentiation of benign and malignant GCTB. In the first case, there are no changes, in the second, an acceleration of ESR, leukocytosis, a decrease in iron and protein, an increase in the level of alkaline phosphatase, phosphorus, and calcium are detected in the blood. Hexokinase and oxyproline are detected in the urine.
The distinction is made with an aneurysmal bone cyst (more often – a solid variant), central giant cell granuloma, chondroblastoma. Differential diagnosis with non-ossifying fibroma and osteosarcoma is also required.
The main method of treatment of GCTB is surgical intervention. The volume of the operation is chosen taking into account the size and prevalence of neoplasia. In cases of an “inconvenient” location (in vertebrae, flat bones) or a minor lesion of tubular bones, excochleation is performed. Neoplasms of medium size are removed by the method of marginal resection. With the involvement of half or more of the diameter or a central location, segmental resection is resorted to. According to the indications, bone-plastic techniques are used to replace the resulting defect. Amputations are rarely required.
With limited pulmonary metastases, partial resection of the lungs is performed. Radiation therapy is indicated for hard–to-reach neoplasms, primarily located in the upper sacrum. The method is also used in case of refusal of surgery, the presence of severe somatic pathology. As part of the combined treatment, it is recommended in the pre- and postoperative period. Remote gamma therapy is most often performed.
The prognosis of a benign Giant cell tumor of bone is quite favorable – after radical excision in compliance with the principles of ablasticity, recovery occurs in most cases. The recurrence rate directly depends on the chosen surgical method, it is 46% after excohleation, 30% after marginal resection and 6.6% after radical resection. With the malignant nature of the pathological process, the five-year survival rate is 35%, after 10 years, 18% of patients remain alive.