Isolated fibromas are relatively rare clinically and were previously thought to be a type of mesothelioma; however, in recent years, based on their differentiated origin, coupled with the many reports of non-mesenchymal sites, they are now unanimously considered to be mesenchymal progenitor tumors, originating from dendritic mesenchymal cells. In clinical presentation, it is often asymptomatic, mostly seen in middle-aged adults, with no significant gender differences, and usually presents as a slow growing mass. As the tumor increases in size it will show symptoms of pressure in the corresponding area, such as cough, pain, dyspnea, pulmonary osteoarthropathy, etc. In rare cases, it can cause paraneoplastic syndrome, such as hypoglycemia due to production of insulin-like growth factor. The CT presentation of isolated fibromas has certain characteristics. The maximum diameter of the mass is more than 9 cm, isolated, with clear and bright edges, shallow lobulation, uniform density or necrosis; the mass protrudes into the chest cavity, and no abnormal changes are seen in the rib cage of the corresponding part of the chest wall; after enhancement, the enhancement is generally moderate, with distorted vascular shadow and “pseudo-envelope sign” in the tumor, etc. The enhancement is usually moderate. Large isolated fibroids need to be differentiated from lung cancer, lung sarcoma and benign tumors in the lung. Lung cancer is most commonly seen in patients over 40 years of age with a history of smoking, and the mass may be lobulated and burred on imaging, often with pleural depression, pulmonary atelectasis, and obstructive pneumonia. Pulmonary sarcoma is mostly seen under 40 years of age, expanding growth in the lung parenchyma, rarely invades or breaks through the bronchial mucosa, imaging shows a solid mass, mostly above 5 cm in diameter, there may be calcification and cavity formation within the mass, mostly limited pleural invasion. Benign lung tumors mostly occur in young adults, often without obvious symptoms, generally as a single round or round-like shadow, slow growth, uniform density, no invasion of surrounding tissues, no close relationship with the pleura, and often no enhancement after enhancement CT. Isolated fibromas have a high recurrence rate and tumor-related mortality, but complete surgery, close postoperative follow-up, and subsequent aggressive treatment can still ensure long-term survival in about 70% of patients, with recurrence occurring within 24 months of initial treatment and a poor prognosis once metastasis develops.