Localized Nodular Hypertrophy Mimicking Rhabdomyoma in the Fetal Heart: Prenatal Sonographic and Pathology Findings

Multiple intracardiac masses (ICM) are considered to be diagnostic of rhabdomyoma often associated with tuberous sclerosis. We describe a fetus with multiple ICM detected by fetal sonography at 18.7 wk gestation. The appearance and number were consistent with leading diagnosis of rhabdomyoma. Due to complications of pregnancy and extreme prematurity, the fetus did not survive. Autopsy showed the cardiac masses to be localized nodular hypertrophy (LNH) of the myocardium. No features of rhabdomyoma or tuberous sclerosis were present. In a review of the literature, similar lesions were reported in a child and two adults, perhaps as localized variants of hypertrophic cardiomyopathy. Our case does not, however, show the histopathologic features of hypertrophic cardiomyopathy. Isolated developmental abnormalities, such as in this case, can have a mass effect mimicking cardiac tumors. At the time of autopsy, the largest mass in the anterior wall of the right ventricle extended to and obstructed the right ventricular outflow tract.