其他摘要:Background: Neuroectodermal Tumors (PNET) are malignant small cells neoplasm mainly occurring in children but can occur at any age. Extensive bleeding into the pleural cavity is rare In Children. Hemothorax would be compatible with a variety of congenital anomalies including sequestration, patent ductus artreiosus, and pulmonary arteriovenous malformation. Case report: A 2.5-years old girl who was known a case of PNET with dyspnea and tachypnea referred to our hospital. The chest X-ray revealed bilateral opacity. After consulting the general surgeon, the bilateral chest-tubes inserted and 200cc blood drained. Discussion: The diagnosis of a hemothorax can be made only by thoracentesis. The symptomatology of the Peripheral Primitive Neuroectodermal Tumors is related to size and their location. We did not find any residue of cancer as a cause of hemothorax, and the hemothorax was not related to side effects of chemotherapy, infection and trauma. Therefore, PNET should be included as a cause of children hemothorax.