Benign tumors of the skeleton of the chest wall include: osteochondroma, chondrosarcoma, osteofibrous dysplasia and ossifying fibroma, osteoma, bone cyst, giant cell tumor, aneurysmal bone cyst, eosinophilic granuloma, and osteoblastoma. 1.Osteochondroma: It is a common benign tumor of rib bone. It occurs mostly at the junction of rib and rib cartilage, or the cartilage part of sternum, and occasionally at the head of rib. It originates from the bone cortex and consists of cancellous bone, cartilage cap and fibrous envelope. It can grow inward and outward and is mostly asymptomatic. It is a painless mass with smooth or nodular surface. Tumors in the head of the ribs may sometimes invade the spine and compress the spinal cord, causing paralysis of the lower extremities. x-rays commonly show a round or cauliflower-shaped mass with sharp borders, a long tip or broad base, and an irregularly calcified cartilage cap. Cancellous bone and cartilage are present within the tumor with irregular hypodense underlying areas and no periosteal reaction. The tumor is often recurring when excision is incomplete and can become malignant, so extensive excision is required. 2. Chondrosarcoma: It occurs in young adults between 20-40 years old, grows slowly, can grow inwardly and outwardly in an expansive manner, is mostly asymptomatic, is lobulated, has a fibrous envelope, occurs from cartilage at the pre-ossification stage or from young and weak chondrocytes, can be malignant, and often occurs at the junction of ribs and rib cartilage. The affected bone may be distended and deformed, and the bone cortex may be thinned. In the exophytic form, a sclerotic dense shadow is formed by the spongy layer and grows outward from the normal bone. If intra-tumoral calcification decreases and osteolysis accelerates, this is a sign of malignancy. It is not easy to distinguish from chondrosarcoma clinically, and it is easy to recur if resection is not complete, so it should be widely resected. The two are clinically and radiographically very similar, so it is not easy to distinguish them. In fact, there is a difference between the two. Osteogenic fibroma is more common in the jaws and less common in the long bones. Conversely, osteochondrofibrosis is more common in the rib cage and can occur singly or in multiple cases. There is also a clear histomorphological distinction between the two. Fibrous trabeculae in osteochondral dysplasia generally do not form lamellar bone, and there are no rows of osteoblasts around the trabeculae. This disease occurs in young and middle-aged people, some with a history of trauma, and is a relatively common benign tumor of the rib. There are no obvious symptoms, but compression of the nerve by the diseased ribs may cause chest pain and discomfort. The tumor is often found on the same side of the skin, with hyperpigmentation or endocrine dysfunction of precocious puberty, called A1bright syndrome. x-ray of both is an enlarged rib lesion, fusiform or round, with thinning of the bone cortex and increased bone density in the lesion area, in which there may be translucent areas. x-ray findings must sometimes be differentiated from aneurysmal bone cysts, such as giant cell tumors. The lesion can be completely cured by removing the lesioned ribs, but if too many ribs are lesioned, it is not suitable to remove all of them. 4.Osteoma: It is a rare benign tumor, usually found in the craniofacial bone, mandible, and also in the ribs. It is common in adolescents and is not very different from normal bone tissue and rarely becomes malignant. The texture is hard and generally asymptomatic. The tumor stops growing on its own when the whole body is mature. If the tumor grows outward from the bone surface in the form of a nodule, it is called an exophytic osteoma (wart); if it grows in the medullary cavity, it is called an endophytic osteoma. X-rays show a limited bony mass, connected to the bone plate, with smooth or rough edges and uniform dense density. Asymptomatic patients may be left untreated, while those with symptoms due to compression of adjacent tissues may be excised with good results. 5.Bone cyst: A single cyst in the rib bone, mostly seen in male adolescents under 20 years old, is a slowly destructive bone tumor. X-rays show irregular oval expansion of the ribs with neat and clear transparent shadows on the edges, passive expansion of the bone capsule wall, no internal sandy calcification points, little new bone growth and bone dense phenomenon. Surgical resection has good consequences. Giant cell tumor: It occurs in the bones of the limbs, but is rare in the ribs, often at the posterior end of the ribs. The most common age of onset is 20 to 40 years old. X-rays show soap bubble-like translucent areas, thinning of the bone cortex like eggshells, and thin bony intervals, which do not spread to the soft tissues, so no soft tissue swelling can be seen. Individuals are rich in blood vessels and can be palpated. The morphology is difficult to distinguish from aneurysmal bone cysts and bony fibrous dysplasia. This tumor is benign, but malignant transformation and distant metastasis can occur, and whole chest wall resection should be performed. 7, aneurysmal bone cyst: Mostly in the vertebrae, flat bone, long tubular bone stem, and also in the ribs, mostly in adolescents aged 10 to 20. The progression is slow, no specific clinical symptoms, there may be a long period of chest pain and discomfort, but also may develop rapidly. The cause of the disease is due to local circulatory disorders, arteriovenous anastomosis and communication within the lesion, elevated venous pressure, massive vasodilatation and congestion in the bone, and destruction of the bone by compression. x-ray shows blowing cystic changes in the ribs, with intervals between the cystic cavities, forming most cystic cavities. On intercostal arteriogram, the veins in the lesion are seen to develop earlier than in other areas, suggesting arteriovenous communication. However, arteriograms are not easily differentiated from other lesions, especially from giant cell tumors. The lesion may recur with scratching and radiation therapy, and surgical excision can cure it. 8. Eosinophilic granuloma: It is not a real tumor of the bone, but a granulomatous lesion characterized by massive tissue cell proliferation and eosinophilic leukocyte infiltration. It is mostly seen in children and adolescents, more in men than in women. It often occurs in the skull, ribs and vertebrae. There is local pain and tenderness, and an increase in eosinophilic leukocytes in the blood (4% to 10%). The lesions are located in the bone marrow cavity and extend into the bone cortex, even invading the soft tissue. The lesions are usually small, from a few millimeters to a few centimeters, soft and brittle, and may have cystic changes. The bone cortex may show lysis defects or pathological fractures. The prognosis of the disease is good, and a few cases can be fully healed by self-resolution. The disease can be treated with radiation therapy for multiple cases. 9. Osteoblastoma: It is rare, and is usually found in long bones and vertebrae, but also in ribs. It is more common in adolescents. The disease occurs in isolation, with abundant blood vessels, bone and bone-like tissue formation, and osteoblasts. The tumor is slowly developing, usually 2-10 cm in size, with hemorrhage and calcification, and the tumor is loose and brittle. x-ray shows a clear demarcation between the tumor and the surrounding tissues, and there is often thickened epiphyseal tissue or osteophytes in the peripheral part of the tumor, and the adjacent bone cortex has different degrees of expansion and thinning, and sometimes pathological fractures may occur. X-rays are often misdiagnosed as osteosarcoma. The differentiating point is that osteosarcoma has typical shadows of tumor neointima, periosteal reaction, and soft tissue masses. This tumor is benign, but it can recur after surgery in individual cases and should be completely excised. Metastasis does not occur.