[Incidental myocardial mass: differential diagnosis, clinical approach and literature review]

A 30-year-old male was evaluated in our hospital for the presence of transient palpitations. The ECG showed sporadic ventricular extrasystolic beats with normal ventricular depolarization and repolarization phases. Two-dimensional transthoracic echocardiography demonstrated a localized intraventricular myocardial mass (measuring 3 x 2 mm) in the basal lateral wall. To further characterize the mass, the patient was addressed to cardiac magnetic resonance imaging (MRI). Noninvasive myocardial tissue characterization with T2-weighted sequences (with and without fat suppression), and T1-weighted after contrast suggested the presence of fat tissue associated with undiversified muscle tissue. The intramyocardial mass was not capsulated and partially infiltrated the surrounding myocardium. The imaging features suggested the diagnosis of a benign myocardial mass with mixed aspects between cardiac hamartoma and lipoma. To monitor mass growth and in the absence of new symptoms, the patient is followed up yearly with transthoracic echocardiography, and with cardiac MRI exams every 3 years. This case highlights the utility of cardiac MRI to assess a myocardial mass noninvasively and delineate its anatomy and tissue characterization, which potentially avoids myocardial biopsy.