BackgroundThe majority of the patients with a solitary fibrous tumor (SFT) of the pleura are asymptomatic, and rupture of an SFT with hemothorax is rare.Case presentationA 48-year-old man was taken by ambulance to our hospital because of sudden onset of left chest pain. Two months before the referral, a tumor was detected in the left upper lobe of the lung by screening computed tomography at another hospital, and further observation was recommended, because the tumor was suspected to be benign. Our contrast-enhanced computed tomography analysis of the chest revealed a solid tumor (5 cm in diameter) with an irregular enhancement effect close to the pericardium and pleural effusion in the left thoracic cavity. Pleural effusion was not detected in the previous imaging analysis. CT number of the pleural effusion was 40 HU, and the pleural effusion was suspected to be hematogenous. Therefore, rupture of the tumor with bleeding was suspected as the cause of the effusion because of the sudden onset. Preoperative diagnosis was a mediastinal tumor, such as a teratoma, because the tumor was close to the pericardium. Thoracoscopic surgery was performed with the patient in the right lateral decubitus position; bloody pleural effusion was observed and drained. The tumor originated from the visceral pleura of the left upper lobe of the lung and was resected with a surgical stapler. Macroscopic analyses of the resected tumor indicated that bleeding were caused by the rupture of the tumor at the defect of the capsule wall. The operation took 63 min. The postoperative pathological diagnosis was a benign SFT. Hemorrhage was observed just under the capsule wall of the tumor. The postoperative course of the patient was uneventful, and he was discharged 2 days after surgery.ConclusionsEven when an SFT is neither huge nor malignant, rupture can occur, and resection should be considered regardless of the size or malignant characteristics. After an SFT rupture, careful follow-up is needed to monitor for the intrathoracic recurrence or dissemination of the tumor.