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 is a common benign tumor of the rib bone. It mostly occurs at the junction of rib bone and rib cartilage, or the cartilage of sternum, and occasionally at the head of rib bone, and grows slowly. 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. Chondrosarcoma occurs in young adults between 20-40 years old, with slow growth, inward and outward expansion, mostly asymptomatic, lobulated, with fibrous envelope, occurring from cartilage or young chondrocytes at the pre-ossification stage, and can be malignant, and often occurs at the junction of rib 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, and they are considered to be the same disease, or osteogenic fibroma is a subclass of osteogenic fibroma. 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 removal of diseased ribs can be completely cured, but if too many ribs have lesions, it is not suitable to remove all of them. 4.Osteoma is a rare benign tumor that occurs in the craniofacial bone, mandible, and also in the rib cage. It is common in adolescents and is not very different from normal bone tissue and rarely becomes malignant. It is hard in texture and is usually 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), and 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 density. Asymptomatic patients can be left untreated, while those with symptoms due to compression of adjacent tissues can be excised with good results. 5.Bone cyst is a single cyst in the rib bone, mostly seen in male adolescents under 20 years old, and is a kind of slowly destructive bone tumor. X-rays show irregular oval expansion of the ribs with neat and clear transparent shadows, passive expansion of the bone capsule wall, no internal sandy calcification points, little new bone growth and bone denseness. There are few new bone growths and bone densities. Surgical resection has good consequences. Giant cell tumor is more common in the bones of the limbs and less common in the ribs, and often occurs at the posterior end of the ribs. The most common age of onset is between 20 and 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 cysts are mostly found in the vertebrae, flat bones, the backbone of long tubular bones, and also in the ribs, mostly in adolescents aged 10 to 20. It progresses slowly without specific clinical symptoms, and may have prolonged chest pain and discomfort, or may develop rapidly. The cause of the disease is due to local circulatory disorders, arteriovenous anastomosis in 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 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 can be cured with surgical excision. 8. Eosinophilic granuloma is not a real tumor of 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 lesion is located in the bone marrow cavity and extends to the bone cortex and even invades 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 radiotherapy for multiple cases. 9.Osteoblastoma is very rare, usually found in long bones and vertebrae, but also in ribs. It is more common in adolescents. The disease occurs in isolation, rich in blood vessels, with bone and bone-like tissue formation and osteoblastoma. 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.