We report the case of a 28-year-old woman taking contraceptives diagnosed with pulmonary embolism with a mass in the right atrium demonstrated by trans-thoracic echocardiogram that was not recognized on a previous angio-CT. Initially, it was thought to be a thrombus, but trans-oesophageal echocardiography and cardiac MRI showed data suggestive of cardiac neoplasm. Pericardial effusion and adjacent myocardial wall thickening noted on trans-oesophageal echocardiography were reported as signs that supported the possibility of malignancy, although cardiac MRI did not show wall infiltration signs. On the contrary, it demonstrated enhancement, which excludes the thrombotic nature of the mass and supports the diagnosis of neoplasm. The patient underwent surgery and biopsy proved that the mass was a myxoma. While myxomas are the most common among primary cardiac tumors, its attachment to the atrium free wall, far from the inter-atrium septum, the bi-lobed shape and accompanying pericardial effusion were atypical.