Atrial pseudothrombus, a new radiological sign of right atrial roof bulging, caused by pericardial effusion, observed on chest CT

A 22-year-old female patient was admitted to the emergency room of an Oncologic center, with an acute onset of dry cough, hyaline runny nose, and sudden, severe, ventilatory-dependent chest pain, located in the parasternal region with shoulder irradiation, followed by dyspnea. On physical examination, associated findings are perioral and on the distal fingers' phalanges cyanosis. There was no history of fever, paresthesias, syncope, or other symptoms. Six years ago, in 2013, she had been diagnosed with 10th right costal arch Askin's tumor with pulmonary metastasis. Initially, she started receiving 1st line chemotherapy according to the Metastatic Ewing Sarcoma Protocol 2010, and then surgical approach for metastatic resection four right costal arches. So far, she has had three relapses, the first in 2016 for the left femur and lungs, in 2017 for the skullcap and 2018 for the right femur and right tibia. Since then, she has been receiving treatment according to an alternative chemotherapy protocol consisting by Topotecan 0.75mg/m D1 to D5/CTX 250mg/m D1 to D5 every 21 days and radiotherapy. A year ago, she developed a chronic thrombosis of the left brachiocephalic vein.