Clinical data The patient, a 53-year-old male farmer, was admitted to the hospital on April 18, 2007 with “recurrent cough and fever for more than 4 months, accompanied by chest tightness for 1 month”. 17 years ago, he had a “history of surgery for extraosseous osteosarcoma of the right upper limb” (details unknown). Chest X-ray and chest CT showed that the right pleural cavity had a large amount of fluid with partial encapsulation changes, the right lung was partially inflated, and the right pleura was calcified. Physical examination: body temperature 37.3℃, generalized superficial lymph nodes were not palpable enlarged, the right thorax was full, the right respiratory motility was reduced, a thin drainage tube connected to a drainage bag was seen on the right thoracic back, and a small amount of yellowish pleural fluid (placed outside the hospital) was visible. The right lung fibrillation was diminished, the right lower lung was turbid on percussion, the right lung breath sounds were low, the left lung breath sounds were clear, no dry wet rales were heard, the heart rate was 82 beats/min, the rhythm was uniform, no pathological murmur was heard, and no pericardial friction sounds were heard. The abdomen was flat and soft, without pressure pain and rebound pain, the liver and spleen were not palpable under the ribs, no mass was palpable, mobile turbid sounds were negative, intestinal sounds were about 4-5 times/minute, and there was no swelling in both lower limbs. The 24-hour ambulatory electrocardiogram showed sinus rhythm and occasional premature supraventricular oscillations, the abdominal ultrasound showed multiple calcified spots in the liver, no obvious occupancy in the biliary, splenic and pancreatic kidneys and adrenal glands, no obvious abnormality in the head CT, the pulmonary function showed moderate restrictive ventilation dysfunction, the blood routine showed WBC8×109/L, HGB127G/L, PLT220×109/L, the liver and kidney function showed The rest were not different. After completing all the investigations, a right dissection and right total pneumonectomy with lymph node dissection were performed under general anesthesia on April 25, 2007. Intraoperatively, he found pleural thickening, extensive adhesions in the chest cavity, about 300 ml of yellow pleural fluid, and a huge mass in the right lung, about 21×17×10 cm in size, with uneven surface, partly hard texture and partly cystic, and the right lung was completely compressed and undilated. The right whole lung was successfully resected intraoperatively. The surgical pathology report was: giant extraosseous osteosarcoma of the right lung, (inferior bullae) 7 (hilar) 3 (parapneumonic) 2 lymph nodes with chronic inflammation and negative bronchial stump. The patient recovered well after surgery, and there is no sign of discomfort or tumor recurrence at follow-up to date. Osteosarcoma can also occur in organs other than bones and soft tissues, which is called extraosseous osteosarcoma (EOS) or soft tissue osteosarcoma, and is a rare and highly malignant soft tissue sarcoma. The pathological signs of this tumor are essentially the same as those of osteosarcoma of bone, which should have tumor bone and bone-like tissue. Microscopically, the tumor cells are spindle-shaped, round or oval in shape, with variable size and irregular morphology. Some of the tumor cells are clustered, with darkly stained cells, large darkly stained nuclei, and frequent nuclear mitoses. There are more multinucleated giant cells with large and malformed nuclei and thick nuclear membranes. The nuclear chromatin is coarse, the number of nucleoli is high, and there is bone-like tissue and naive cartilage present. The incidence of EOS is low, accounting for only 1.2% of soft tissue sarcomas and 3.7% to 4.6% of osteosarcomas. Unlike osteosarcoma, which is more common in adolescents, EOS is more common in middle-aged and older patients, with a mean age of onset of 50.7-54.6 years, and no significant difference between men and women. The disease most often involves the extremities, with the lower extremities accounting for 46.6%, the thighs and buttocks most likely to occur, and the upper extremities accounting for 20.5%; other trunk, thoracic (heart, lung, pleura) and intra-abdominal cavities are rare. eos is highly susceptible to local recurrence and distant metastasis, with Lee having reported a recurrence rate of 45% and a metastasis rate of 65%, with recurrence and/or metastasis generally occurring within 3 years of diagnosis. The most common site of metastasis is the lung, followed by regional lymph nodes, bone, liver, and heart. The typical presentation can be seen as a high-density shadow formed by cords or blocks of dense tumor bone or some bone pins in the periphery, mostly in the form of cotton wool or plaques. The diagnosis still requires biopsy or postoperative pathology. The patient in this case had a history of surgery for extraosseous osteosarcoma of the right upper limb 17 years ago, and this intrapulmonary tumor should be considered as both metastatic and primary. The tumor was huge and the surgical exposure was difficult. Postoperatively, the patient recovered well and has no discomfort so far, and the surgical value is high.