BACKGROUND Epithelioid sarcoma is a rare tumor and that is extremely rare as a primary pleural neoplasm. On imaging, it may appear similar to malignant pleural mesothelioma; thus, it can be difficult to diagnose. CASE REPORT A 64-year-old Asian woman, who had a treatment history of cervix adenocarcinoma, was admitted with dyspnea and right massive pleural effusion. Chest drainage was performed, and malignant cells were found in the pleural effusion. The malignant cells were thought to be metastasized from previous cervical cancer. We continued pleural drainage; however, the volume of the pleural effusion did not decrease. On the 5th hospital day, the chest tube became occluded. Computed tomography showed structures similar to empyema. Pleural irrigation and fibrinolytic therapy did not improve her condition. Empyema curettage was performed on the 14th hospital day. The resected pleura was submitted for pathological examination and showed tumor lesion but not metastatic adenocarcinoma of the cervix. The intrathoracic tumor grew extremely rapidly, and the patient died of respiratory failure on postoperative day 8 (22nd hospital day) before a diagnosis could be made. The final pathological diagnosis obtained on the 34th hospital day was epithelioid sarcoma. CONCLUSIONS For patients who appear to have empyema complicated by neoplastic lesions, a histopathological examination should also be performed to ensure accurate diagnosis. In addition, if a tumorous lesion is detected and it is neither metastatic nor malignant pleural mesothelioma, pleural epithelioid sarcoma should be added to the differential diagnosis in the presence of a rapidly growing and histologically difficult-to-diagnose pleural tumor.