Left atrial primary intimal sarcoma mimicking myxoma: case report.

Background: Primary malignant cardiac tumours are very rare, with a reported incidence ranging from 0.0017% to 0.07%. Intimal sarcomas originate from subendothelial multifunctional stem cells and occur predominantly in older individuals, affecting large arteries. Cardiac localization is extremely rare. Case summary: The case report describes a 74-year-old woman with a history of stroke and paroxysmal atrial fibrillation. Echocardiography and computed tomography showed a large left atrial mass extending into the mitral orifice. Tumour lobes partially extended into the left atrial appendage and the left superior pulmonary vein. Despite diagnostic uncertainty, the therapeutic strategy remained unchanged, and surgical resection was indicated. Surgical intervention revealed a tumour infiltrating the posterior wall of the left atrium, consistent with intimal sarcoma. The diagnosis was confirmed by histological examination demonstrating high mitotic activity and specific immunohistochemical markers. Discussion: Echocardiography is the most commonly used imaging method for diagnosing cardiac tumours, with a sensitivity of 93% for transthoracic and up to 97% for transoesophageal echocardiography. Features suggesting a higher risk of malignancy include a tumour larger than 50 mm, involvement of more than one heart chamber and/or the pericardial space, haemorrhagic pericardial effusion, and exophytic masses with a broad base arising from the cardiac chamber wall. Magnetic resonance imaging and positron emission tomography may further contribute to the differential diagnosis of malignant primary cardiac tumours.