Giant cell tumor of bone originates from the non-osteogenic connective tissue of bone, and the main components of the tumor are giant cells similar to osteoclasts and round and spindle-shaped stromal cells. Because its main components are similar to osteoclasts, it is also called osteoblastoma. I. Pathology Jaffe believes that osteoblastoma occurs in the mesenchymal cells within the bone marrow. Grossly anatomically, the tumor can be seen to occupy a part or a large part of the end of the bone, and the adjacent bone cadres of the tumor consists of soft and brittle Dan easy to hemorrhage granulation tissue, no fibrous envelope. When the tumor bleeds, it is brown or red. The hematoma is grayish-white after mechanization. When the tumor becomes necrotic, it is black and yellow. Within the areas of excellence and necrosis, there may be cystic changes, with the capsule containing mucus or blood. The tumor itself is often separated by connective tissue septa. The adjacent bone cortex swells and thins, forming an incomplete and thin bone shell; the tumor may also penetrate the bone shell and grow into the soft tissue, sometimes with a peripheral membrane, sometimes infiltrating the surrounding tissue. There is often a thin layer of reactive new bone around the tumor. The articular cartilage is often not invaded. Microscopically, osteoblastoma is mainly composed of giant cells and stromal cells. Giant cells are large and multinucleated, with an average of 20-30 nuclei and up to 100 nuclei. The stromal cells are round or spindle shaped, and besides fusing into giant cells, they can differentiate into phagocytes, fibroblasts or osteoblasts, i.e. they are pluripotent. If the typical giant cells decrease or disappear, and the stromal cells are disorganized, tightly packed, increased in number, and of different shapes and sizes, then it is considered a malignant giant cell tumor. Histologically, giant cell tumors are generally divided into three grades: Grade I: benign giant cell tumor, containing giant cells of large size, high number, uniform distribution, the number of nuclei is generally on the 50, and nuclear division is occasionally seen. The stromal cells are mainly spindle-shaped, with abundant cytoplasm, different sizes of cytomembrane, light staining, loose distribution, not bundled or rotating vortex. Grade II: Giant cell tumor with malignant tendency, stromal cells are tightly arranged and become bundled or rotated vortex. The nuclei are large and different in shape, and nuclear division can be seen. The number and volume of giant cells are reduced and unevenly distributed, and the nucleus of the thoracic cells is enlarged, scanty in number and deeply stained. Grade III: malignant giant cell tumor with tightly arranged and disorganized stromal cells, few cytoplasmic cells, and different shapes. The nuclei are enlarged and increased, with deep staining and many nuclear divisions. Giant cells are small in size, few in number, unevenly distributed, with enlarged thoracic nuclei, scanty in number and deep in staining. Age of onset Young adults aged 20-40 years old account for more than 80% of the total number of cases, while those under 20 years old and those over 40 years old are rare, and those under 10 years old are even rarer, and the incidence rates of men and women are roughly equal. Common Symptoms: ①Pain and swelling at the tumor site, the pain is aggravated after activity and alleviated after resting, and the pain becomes persistent when bone destruction is obvious. When bone destruction is obvious, the pain will become persistent. ②Tumor has the characteristics of latent growth, and often no obvious symptoms are found before it grows to a large size. After the tumor grows up, it can cause dysfunction of bones and joints. Muscle atrophy is also common. In advanced cases, there is a “popping” sound or a feeling of pressing a ping-pong ball when palpation is made, or even a throbbing sensation. In some cases, the disease is not recognized until the patient has a pathological fracture. Bone giant cell tumor mostly occurs in the bone end of mature bone after epiphyseal fusion. Early stage: eccentric bone destruction area is often seen at the end of long tubular bone, which is round or oval in shape. The tumor lacks a sharp boundary with the surrounding and appears blurred, there is no infiltration around the tumor, and its adjacent cortex may be thinned by swelling, but it is not accompanied by periosteal reaction. At this time, in the center, it is not always possible to show the bony septum. 2.Due to the enlargement of the tumor, it expands to the periphery, and its expansion speed to the end of the bone is more significant than that to the bone cadre, and the tumor can be expanded all the way to the lower part of the joint, and the degree of its transverse and longitudinal expansion is similar, sometimes the transverse direction is even more than the longitudinal direction, which is not easy to see the phenomenon of transverse obvious expansion in other bone tumors. 3.This tumor does not invade the joints, the lesion in the central area of the bone ends stops progressing when it reaches the lower part of the articular cartilage, while the lesion in the marginal part of the bone ends continues to develop, thus relatively plunging the shadow of the joints into the shadow of the tumor, similarly, in the part of the tumor and the backbone, the tumor can also be rapidly enlarged and expanded, thus burying part of the backbone in the shadow of the tumor. 4.The foam translucent area in the center of the tumor is the typical manifestation of giant cell tumor. The formation of foam shadow is the overlapping projection of the residual fractured bone cortex around the tumor or the bone ridge and bony intervals formed in the cortex. 5.In a very few cases, the giant cell tumor lesion may exceed the joints and involve the adjacent bones, for example, the lesion of the upper end of femur may exceed the patellar joint and involve the iliac bone of the same side, and the giant cell tumor of spine may exceed the intervertebral disc and involve the adjacent vertebrae. 6. Rapid enlargement of the tumor, worm-like destruction of the cortex of the nearby bones, and absorption and destruction of the calcified tumor or ossified part of the tumor are all indications of malignancy or malignant transformation. Differential diagnosis (a) bone cysts are common in children and young people, the lesion is located in the metaphysis of humerus, gradually to the bone regression, its expansion to the surrounding is not as obvious as the giant cells, multi-compartmental bone cysts can have residual bone trabeculae, but it is not easy to see the typical foamy image. (II) Benign chondroblastoma, the patient’s age is usually below 30 years old, and it occurs in the long epiphysis of the limbs. X-ray manifestation shows that there are flocculated or sand-like calcified spots in the translucent area of the tumor, which is different from that of giant cell tumor of bone. (C) Hyperparathyroidism: the lesions are characterized by localized bone expansion, bending deformity, generalized osteoporosis, cortical thinning and subperiosteal resorption. Laboratory examination of blood calcium, phosphatase increased, blood phosphorus decreased.