Enchondroma is a benign tumor of hyaline cartilage tissue that occurs in the bone marrow cavity. Enchondroma is relatively common, accounting for 10% to 25% of benign bone tumors, and is the most common bone tumor of the hand. The incidence of endogenous chondrosarcoma is equal in both sexes. It can be solitary or multiple. Multiple cases are also called endogenous chondromatosis (including Ollier’s disease and Maffucci’s syndrome). The combination of endogenous chondromatosis with bone malformations is called Ollier disease; the combination of endogenous chondromatosis with soft tissue (and occasionally visceral) hemangiomas of the limbs is called Maffucci’s syndrome. Endogenous chondromatosis is rare, commonly seen in children, and often involves a wide range of bones, often with symmetrical growth on one or both upper and lower extremities. All endogenous chondromas occur at the site of chondrogenic bone. They are commonly found in the hands and feet and often involve small tubular bones. The distribution in the hand is characteristic, most often in the proximal phalanges, followed by the metacarpals, middle phalanges, and distal phalanges. Long tubular bones (especially the proximal humerus and the proximal and distal femur) are next in importance. Flat bones (pelvis, ribs, scapula, sternum, spine, etc.) are uncommon. Craniofacial bones are rare. Clinical manifestations Endogenous chondrosarcoma is slow growing, small in size, and can be asymptomatic for a long time, and is often detected only at an older age; therefore, it can be seen clinically in any age group, and is most common between the ages of 10 and 50. Endogenous chondromas in tubular bones of the hands and feet often lead to deformities of the fingers or toes and are often painful due to local swelling and irritation of the bone, or due to pathological fractures. In the long tubular bones, most endochondromas are asymptomatic and are detected only on radiographs due to other diseases or pathologic fractures. In contrast, endogenous chondromas can show signs and symptoms in early childhood and can lead to limb shortening and curvature deformities. In the hand, the lesion is spherical or nodular and swollen. In severe cases, the fingers are shortened and deviated from the axis, usually without pain. There is slight swelling in the epiphysis of the limb, with shortening deformity as the bone develops. Imaging diagnosis Endogenous chondrosarcoma appears as a well-defined, swollen area of bone destruction on x-ray, and the surrounding bone can have a sclerotic rim. The tumor is usually located in the central part of the backbone, and the bone cortex may appear distended and thin. If the tumor is located on one side, it can cause extreme cortical thinning. Endogenous chondrosarcoma can have varying degrees of calcification, manifesting as punctate, flocculent, annular, and arcuate. In adult patients, signs of calcification are diagnostic radiological features of endogenous chondrosarcoma. Endogenous chondrosarcomas tend to be small. If the tumor is larger than 5 cm in the medial or flat bone, one should be alert to the possibility of chondrosarcoma. CT is sensitive to detect calcification within the tumor, which is of special value for diagnosis, and calcification within the cystic translucent area is considered to be the main basis for diagnosis.CT has obvious advantages in showing endogenous chondrosarcoma of long bones, which can clearly show the lesion in the medullary cavity as lobulated, round-like bone destruction or swelling bone destruction, and the occurrence of swelling bone destruction can be observed as thinning of bone cortex and whether the bone cortex is continuous. MRI can show the extent of the lesion in the medullary cavity very clearly. On T2WI, endogenous chondromas show lobulated high signal, which reflects the high ratio of water content to mucopolysaccharide component within hyaline cartilage. Isotope scan During the growth phase, the isotopic uptake of active endophytic chondroma increases, but the uptake of isotopes from its adjacent epiphyseal plate also increases, and the two are not easily distinguished when they overlap. As the skeleton matures, the concentration of nuclei indicates the presence of chondrogenic endochondral bone around the lobulated lesion. Pathologic diagnosis Gross examination Endogenous chondromas are generally small, usually less than 3 cm, and the tumor tissue consists of bluish-white, firm or slightly mucinous hyaline cartilage that is lobulated and contains dull white cartilage and yellow gritty tissue that is highly calcified or ossified cartilage. The edges of endogenous chondroma are irregular and the tumor can spread along cancellous bone crevices and erode the bone cortex, so tumor tissue is easily left behind when endogenous chondroma is scraped. Microscopic examination Chondrosarcoma has little cellular component, lacks vascularity, and is accompanied by a large amount of hyaline cartilage matrix. Chondrocytes are located in sharp-edged sockets with blurred cell outlines, pale pulp color, and often vacuolated, small, densely stained, round nuclei. Treatment of endogenous chondrosarcoma should depend on the presence of symptoms. If there is no symptom, it can be left untreated. If local pain occurs, or if it compresses the surrounding blood vessels or nerves and affects the function of the joint, then surgery can be performed. The usual surgical method is to scrape and remove the bone graft. The sclerotic edge should be scraped together during surgery, and the residual cavity should be treated with anhydrous ethanol and carbolic acid to reduce postoperative recurrence, and autologous bone, allogeneic bone or artificial bone should be implanted in the cavity. For endogenous chondrosarcoma in long tubular bone, if it is asymptomatic and calcified, it can also be observed. If there are symptoms and osteolysis, the possibility of sarcomatous transformation should be considered. Preoperative biopsy is recommended to clarify the diagnosis. Extensive resection should be considered for recurrent cases. Prognosis The prognosis for solitary endophytic chondrosarcoma is good, with rare local recurrence after complete curettage. About 1/3 of endogenous chondromatosis occurring in the pelvis or scapula may malign into chondrosarcoma.