Masses left behind by healed tissue after a fracture or by certain diseases such as bone tumors are called skeletal masses. The skeletal system, like other organs, can develop tumors from any tissue component or metastatic lesions from other organs. Tumors that invade the bone can occur in the bone cells, the hematopoietic component of the bone, the cartilage, and the fibrous or synovial component. Other tumors may arise from the muscles and nerves, blood vessels, and fatty tissue of the bone. Bone masses may not be felt at first, but may become swollen and painful when the mass is larger. The affected area is painful, and there are localized lumps and swelling in the joints and limbs. The movement of the affected joints and limbs is limited. Localized bones are often found in the flat bones, especially in the sternum, ribs, skull, clavicle, and mandible, etc. Localized bones are elevated, hard to touch or rubbery and soft to the touch, with elasticity or sound when pressed, and localized pressure pain. Tumor tissue commonly infiltrates nearby soft tissues, and bead-like changes in the sternum, ribs, and jawbone junction are seen in half of the patients. The following diseases may cause skeletal masses: 1. Aneurysms are classified as true, pseudo and intercalated aneurysms, mostly due to arteriosclerosis or trauma, and syphilitic is rare. They can occur in the carotid artery, subclavian artery, axillary artery, brachial artery, radial artery, iliac artery, femoral artery and naive artery, with the femoral artery and naive artery as the preferred sites. Multiple myeloma (MM) is the most common type of malignant plasma cell disease, also known as myeloma, plasma cell myeloma or Kahler’s disease. It was not until 1889, when Kahler reported cases in detail, that multiple myeloma became generally known and recognized. Multiple myeloma is characterized by malignant proliferation of monoclonal plasma cells and secretion of large amounts of monoclonal immunoglobulins. The incidence is estimated to be 2-3/100,000, with a male-to-female ratio of 1.6:1. Most patients are >40 years old, and black patients are twice as likely as whites. Meningioma is divided into intracranial meningioma, which is formed by intracranial arachnoid cells, and ectopic meningioma, which refers to meningioma occurring in tissues and organs not covered by meninges, mainly evolving from the arachnoid tissue left in embryonic period. The preferred sites are the scalp, skull, orbit, sinuses, trigeminal hemimelia, and the outer layer of the dura mater. Among intracranial tumors, meningioma is the most common benign intracranial tumor after glioma, accounting for 15% to 24% of intracranial tumors. 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 others, 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 the bone, occasionally they occur in the bone stem or epiphysis. 5. Giant cell tumor of bone Giant cell tumor of bone was first discovered by Jaffe in 1940 and is one of the common primary bone tumors. Giant cell tumor of bone is highly aggressive and has a high lytic and destructive effect on bone. Very rarely, it has a tendency of reactive new osteogenesis and self-healing, and can cross the bone cortex to form soft tissue masses. Giant cell tumor of bone is a low-grade malignant or potentially malignant tumor. 6. Fracture A fracture is a complete or partial break in the continuity of a bone structure. It is mostly seen in children and the elderly, but it also occurs in young and middle-aged people from time to time. Patients often have a single fracture, but a few have multiple fractures. After timely and appropriate treatment, most patients can recover their original function, but a few patients may have different degrees of sequelae.