Hamartoma of mature cardiac myocytes: a case report.

A 24-year-old man presented with hypertension, palpitations, and premature atrial and ventricular contractions. A mass was discovered in the distal interventricular septum that was composed of dense collagenous tissue, fat, and disorganized, hypertrophic, mature cardiac myocytes indicative of a cardiac hamartoma. This entity has only rarely been reported and must be distinguished from the much more common rhabdomyoma and from oncocytic cardiomyopathy, which is also referred to as "cardiac hamartoma."