The clinical presentation and the histological appearance of primary cardiac tumors varies greatly. While a majority of them presents with non-specific or insidious symptoms or as incidental findings, still others may present with acute symptoms necessitating emergency surgery. For an appropriate surgical planning, a precise preoperative diagnosis of cardiac tumors and their distinction from thrombi and other tumor-like lesions is mandatory. Echocardiography, CT and MRT are the most useful diagnostic tools in the assessment of cardiac tumors, which in almost all cases precisely locates the tumor and defines its extent and thus resectability [4
]. Atrial myxoma usually measures a few centimeters when diagnosed. However, several cases of huge atrial myxomas have been reported [5
]. Most of these unusually giant myxomas have been associated with mechanical complications that resulted in acute and life-threatening cardiac symptoms. On the other hand, huge but asymptomatic atrial myxoma is uncommon [5
]. Huge myxomas commonly undergo variable degrees of regressive changes with evidence of old and recent haemorrhage. Occasional cases my display unusual regressive changes including osseous metaplasia. These changes might be so extensive that the lesion closely mimics a large organizing thrombus and the neoplastic nature of the lesion might be recognized only after thorough sampling of the specimen. On the contrary, large mural atrial thrombi my occasionally closely mimic myxomas [10
In summary, we described the clinical features, imaging characteristics and histopathological findings in an unusual case of huge atrial myxoma that caused acute cardiac symptoms as a result of prolapsing into the mitral valve. This unusual presentation of atrial myxoma needs be included in the differential diagnosis of atrial thrombi and other causes of acute-onset cardiac symptoms associated with mass-occupying lesions in the heart.