A 54-year-old patient seeks medical assistance complaining about lumbar pain, shortness of breath during ordinary activities, palpitations and an 11kg (24lb) weight loss in the last 6 months. History of pulmonary histoplasmosis in 2008, HIV negative, treated with anfotericin B. At examination, he had palpable right ventricle (RV) on left lower sternal border, as well as an ejective systolic murmur audible on pulmonic area and left lower sternal border. A transthoracic echocardiogram was performed showing a well delimited mass with vesicular aspect on RV, causing valvar stenosis and obstruction of the RV exit. Later, a magnetic resonance (MR) was taken.

Question:
Based on the clinical history and on the images provided, which is the most probable diagnosis?