[Exceptional cardiopulmonary triad revealing an endometrial stromal sarcoma].

A 27-year-old woman presented with right proximal pulmonary embolism associated with thrombosis of the right inferior pulmonary vein extending into the left atrium as an atrial mass. The etiological work-up revealed a BCOR-rearranged endometrial stromal sarcoma. Clinical evolution was favorable under anticoagulation, except for the atrial lesion, whose thrombotic or tumoral nature could not be definitively established despite multimodality imaging. This clinical case highlights the limitations of noninvasive characterization of intracardiac masses in an oncologic setting and their impact on therapeutic decision-making.