Rare Case of Grade 3 Undifferentiated Pleomorphic Sarcoma in Left Atrium, Mitral Valve, and Papillary Muscle.

: Primary intracardiac tumors may be diagnosed incidentally, sometimes in the case of complications. : This case report presents a 64-year-old woman who was admitted to the emergency department with cardiac complications, including heart palpitations and shortness of breath. Initial investigations revealed the presence of ground glass opacity in the left lung and significant mediastinal adenopathy. Transthoracic echocardiography (TTE) indicated severe mitral stenosis caused by a mass attached to the mitral valve, and the transesophageal echocardiography (TEE) confirmed the presence of a tumor, raising concerns about a myxoma with a high risk of embolism. The patient experienced transitory neurological dysfunction, and subsequent imaging uncovered a thrombus occluding the left internal carotid artery. An emergency surgical procedure was performed, including extracorporeal circulation and rapid deep cooling, to facilitate safe mass excision and carotid embolectomy. Histopathological analysis of the extracted tissue revealed undifferentiated pleomorphic sarcoma (FNCLCC Grade 3). Following the surgery, the patient needed extended mechanical ventilation and subsequently underwent a tracheostomy because of her ongoing respiratory support requirements. : Despite the complexity of the surgical intervention, the prognosis remained poor due to the aggressive nature of the tumor and neurologic complications. This case underscores the rarity of primary cardiac sarcomas, the challenges in diagnosis, and the need for prompt surgical intervention to mitigate risks associated with embolic events.