Extraskeletal masses are chondrosarcomas. Central chondrosarcoma is a chondrosarcoma that originates from within the bone. The main symptom is deep pain that is not intense and non-persistent. In the progressive stage of the tumor, large spherical extraosseous masses may form. There are distinct sites of predilection, in order of predilection, for the femur (especially proximal), pelvis, proximal humerus, scapula, and proximal tibia. The other bones of the trunk, the radius, the ulna, the foot, and the hand (chondromas are more common in the hand and less common in the bones of the trunk) are the less frequent sites of softness. The following diseases are also causes of extraosseous masses: 1. Osteosarcoma Osteosarcoma is a malignant connective tissue tumor in which tumor cells can directly produce tumor bone and bone-like tissue. Its incidence occupies the first place among primary malignant tumors. This tumor is highly malignant and has a very poor outcome. Pulmonary metastasis can occur within a few months, and the survival rate is only 5-20% in 3-5 years after amputation. The lower femur and upper tibia account for about three-quarters of all osteosarcomas, while other places such as the humerus, upper femur, fibula, spine, and ilium may also occur. Most of them are osteolytic, but a few of them are osteogenic. Age of onset: it can occur at any age, but most of them are between 10 and 25 years old, with more males. Most of the tumors are at the end of bone, occasionally they occur in the bone stem or epiphysis. 2.Osteochondroma Osteochondroma is a common benign bone tumor in childhood, usually located in the epiphysis on one side of the bone cortex, growing towards the bone surface, also known as exophytic bone warts. The latter has a genetic predisposition and affects the development of the epiphysis or produces limb deformities, called multiple hereditary osteochondromatosis, or osteochondral continuity. The lesions are located in the epiphysis. The distal femur, proximal tibia and proximal humerus are the most common. Clinically, osteochondromas are painless or painful, but produce symptoms when nerves are compressed. Osteoid osteoma Osteoid osteoma is a benign osteogenic tumor, which is composed of osteoblasts and the bone-like tissue they produce. It accounts for about 1% of all bone tumors and 10% of benign bone tumors. The lesion is a small nest of tumor surrounded by many mature reactive bones. 4.Chondrosarcoma Chondrosarcoma is one of the common malignant bone tumors, which occurs in the medullary cavity as the central type, and in the periosteum as the periosteal type, and a few other tumors may occur in soft tissue. The tumors are found in the long bones of the extremities and pelvis, but also in the vertebrae, sacrum, clavicle, scapula and foot bones. The latter can be caused by the malignant transformation of chondrosarcoma and osteochondroma, which is one of the reasons for the later age of onset. The disease is mostly seen in adults and is rare below the age of 30 years, with a gradually increasing incidence after the age of 35 years. It is more common in males than females. 5. Central chondrosarcoma Central chondrosarcoma is a sarcoma whose cells tend to differentiate toward cartilage. It is divided into: central chondrosarcoma; peripheral chondrosarcoma; and periosteal chondrosarcoma. Treatment is surgical only, which has a fairly high cure rate, and radiotherapy and chemotherapy are ineffective for chondrosarcoma. Because of the slow growth of chondrosarcoma, local recurrence and metastasis can still occur more than 10 years after the resection of the primary tumor. Multiple endogenous chondrosarcomas Multiple endogenous chondrosarcomas were first described by Ollier in 1899, so it is also called Ollier’s disease. It is a rare non-genetic benign tumor. It is often a majority of asymmetrically distributed foci of cartilage and subperiosteal deposits within the bone. It can develop in both long and short tubular bones and can occur unilaterally or bilaterally in the limb.