Isolated endophytic chondrosarcoma is a more common tumor that can occur at any age, but is less common in patients younger than 14 years and older than 50 years. It has the second highest incidence of benign bone tumors, accounting for 15% of cases, with a mean age of 27-47 years. There is no gender difference. It is most commonly seen in limb bones, with finger bones and metacarpals being the most common, followed by humerus, femur, toe, metatarsal, tibia, fibula and ulna. Endogenous chondromas are rare in bones other than the limb bones, with the ribs or sternum being the more common of the rare sites, and the pelvic bones and spine being only rarely reported. The clinical presentation begins with the patient not feeling the presence of the tumor. The earliest attention is drawn to the injury. After injury, there is localized pain and swelling. x-rays may show pathological fractures. It has been reported that 38.4% of endogenous chondrosarcoma cases are detected only when a pathologic fracture of the affected bone is present, while 11% of patients are found incidentally. Some patients may be found to have swelling for a long time, but no pain, or only minimal pain, or intermittent pain. Only after the injury does the pain become apparent. On palpation, the swollen finger bone feels firm; if there is a fracture, severe localized pressure pain and heat may occur. Endogenous chondromas in long tubular bones can exist for a long time without symptoms; therefore, many of these cases are found to have many calcified areas on x-ray. The growth of endogenous chondromas is very slow and symptoms appear well after the actual presence of the tumor. Symptoms occur primarily after injury, and x-ray examination reveals a sparing lesion. If an endophytic chondroma of long tubular bone is painful at the outset without obvious injury, the possibility of malignant transformation should be considered. The radiographic presentation is an oval osteoporotic shadow within the diaphysis that rarely reaches the epiphysis. When the lesion is in the center of the diaphysis, the cortical expansion is not obvious, but if it is on one side, the cortical thinning and expansion is obvious. The osteoporotic area is cloudy and may be interspersed with intervals or punctate densities of increased depth. Such calcified and ossified lesions are further indicative of endogenous chondromas. Isolated endogenous chondromas occur primarily in the phalanges. If there is a lesion in the middle or proximal phalanx of the finger, along with the radiographic findings described above, it is almost certainly a benign endophytic chondroma. CT is used for further evaluation in the absence of significant calcification within the tumor and where the integrity of the bone cortex is unclear or irregular. MRI is useful to show the non-calcified cartilage within the tumor, the extent of the lesion, the presence or absence of penetration of the bone cortex, and tumor invasion of the soft tissue. Chondrosarcomas show low signal on T1-weighted images and significant high signal on T2-weighted images, similar to the signal of hyaline cartilage. Injection of Gd-DTPA enhancement can better show the lesion and improve the accuracy of diagnosis. Pathological manifestations: For tumors, while ancillary examinations are important, the final diagnosis must pay more attention to pathological findings. The pathological manifestations of isolated endophytic chondrosarcoma are highlighted below. The specimen of endogenous chondromatosis scraped out from surgery includes bone cortical fragments and scraped out tumor tissue. If the bone cortex is inflated, the bone cortex fragment is thin and shell-like, which is mostly seen in finger bone, metacarpal bone and metatarsal bone. If the cortex is not expanded, such as in long tubular bones, there are erosive cristae and grooves on the medullary surface of the cortical fragments. The epiphyseal membrane is generally smooth, with no new bone deposits on the surface. If fractures have occurred at the tumor, the bone surface may have crust formation and be uneven. The tumor tissue is blue-white, firm or slightly mucous-like hyaline cartilage containing dull white cartilage and yellow gritty tissue that is highly calcified or ossified cartilage. Some of the scrapings were mainly calcified and ossified cartilage with only a very small amount of hyaline cartilage. Endogenous chondromas of long tubular bones generally have more significant calcification and ossification, but in some middle-aged lesions of phalanges and metacarpals, significant calcification and ossification may also occur. 2.Microscopic examination: microscopically, the tendency of cartilage lobularity can be observed clearly, and cartilage lobules are separated by fissures. If comparisons are made in different fields of view, it is not difficult to speculate on the evolution of such fissures. They form at the site of enlargement and fusion of the chondrocyte crypt, where there is a concomitant disintegration of the cells. This void is finally invaded by blood vessels. At the edge of the void, calcification or ossification may occur and may even contain fat or medullary marrow. In different benign endogenous chondromas, the cells vary in number. Some are rich in cells, while others have areas of sparse cellularity mixed within areas of abundant cells. In fact, endophytic chondromas are not as cell-rich as chondrosarcomas, and in addition, benign isolated endophytic chondromas contain much fewer cells than multiple endophytic chondromatoses. The intercellular material (i.e., stroma) of the lesion may be hyaline, edematous, or mucinous. If the stroma is hyaline, the chondrocytes are often located in crypt foci. The crypt is usually large and contains mostly one cell, but may contain two cells or occasionally a group of cells. If the stroma is edematous or mucinous, the chondrocytes are usually no longer in the crypt and their cytoplasm is multipolar or stellate. Early in this degenerative process, colloid fibers are exposed and the stroma has a tendency to stain eosinophilically. In hematoxylin-stained sections, the stroma may appear smudgy blue if there are deposits of small calcareous particles. If calcification is significant, the granules are particularly evident around the crypt, as well as around the cartilage lobules, especially in the vicinity of the interlobular vascular spaces. If calcification is significant, progressive necrosis of the chondrocytes may occur, or even complete disappearance. Areas of high calcification, especially at the margins of the intervascular space, may ossify through chemosis. When determining whether a chondrogenic tumor is benign or malignant, attention should be paid to the cellular composition, especially to some healthy areas with less significant calcification, and tissue close to the fracture zone should be avoided during the examination. In representative areas of definitely benign endogenous chondrocytes, the chondrocytes are always small, the cell pulp is light-colored and often vacuolated, and the cell outline is blurred. The nuclei are small, round, and darkly colored. Essentially all chondrocytes in benign endophytic chondromas exhibit the above, regardless of whether they are located in the crypt or whether the latter is enlarged. A careful search may reveal individual cells containing binucleated nuclei, which are small but still binucleated. Such binucleated chondrocytes are in a mitotic state. Within benign endophytic chondromas, the presence of mitosis within the chondrocytes is generally not seen. In summary, the cellular features that mark a tumor as benign are small chondrocytes and a majority of mononuclear cells. Malignant transformation of endogenous chondrosarcoma: Any endogenous chondrosarcoma occurring in finger bone, metacarpal bone or metatarsal bone will rarely develop malignant transformation. Malignant changes are mostly seen in endogenous chondrosarcomas within long tubular bones. In the benign stage, this tumor can be asymptomatic. Before turning malignant, endogenous chondromas can have extensive calcification and ossification. The transformation of benign endogenous chondrosarcoma to chondrosarcoma is slow. Cytologically, there are definite changes at the beginning, but this is scattered, so when examining this type of tumor, one should note whether there is an increase in cells, the presence of widely distributed binucleated cells, and hypertrophy of the nuclei. Even if this condition is scattered, if several binucleated chondrocytes are found in one field of view, especially if the giant chondrocytes contain large nuclei, or several nuclei, or many chromosomal clumps, they should not be considered benign. Much has been said above about the various aspects of the presentation of isolated endogenous chondrosarcoma. Next, we will discuss the treatment of isolated endophytic chondrosarcoma. Treatment of this disease should be based on the presence of symptoms. If local pain occurs, or if it compresses the surrounding blood vessels or nerves and affects the function of the joint, it can be surgically removed. The usual surgical procedure is scraping and implanting autologous or allogeneic bone in the cavity. For endogenous chondrosarcoma in long tubular bones, the possibility of sarcomatous transformation should be considered if symptoms occur. For most endogenous chondrosarcomas, scraping and placement of autologous or allogeneic bone alone is sufficient. Radical surgery should be considered in patients with recurrence, which will be determined by the site of disease and the presence of malignant changes. Segmental resection with a large bone graft may be considered for some areas. Microwave inactivation with bone grafting may also be used for malignant endogenous chondromas.