Primary cardiac tumors are exceedingly rare, with an incidence as high as only 0.19%. Up to 75% of these tumors are benign [1]. Of these benign tumors, hamartomas of mature cardiac myocytes (HMCM) are even more rarely encountered, with only 21 cases documented up through 2011 [2]. HMCM occurs due to hypertrophy of cardiac myocytes, which proliferate in disorganized arrangements such as herringbone, haphazard, pinwheel, or whorled histologic patterns. While interstitial fibrosis is frequently observed, inflammation and calcification are not [3].

Typically arising from the left ventricular free wall, they have also been observed less frequently on the septal side, as well as on the right ventricular free wall and right atrium. They have been reported in patients as young as six months and as old as 76 years old [4]. Perhaps arising from the anomalous development of embryonic cells, many patients present without cardiac symptoms and are incidentally found on cardiac imaging [5], and may only have evidence of cardiac pathology via electrocardiography. Other patients may present with dyspnea, chest pain, incessant ventricular tachyarrhythmias, and even sudden cardiac death [6].

As accessibility to echocardiography and cardiac magnetic resonance imaging becomes more widely available, the frequency at which these neoplasms are identified may become more common. Thus the diagnosis and management of HMCM needs to be evaluated and updated. Here we present the first systematic review of the literature surrounding HMCM.