We report echocardiographic findings of an intracardiac mass in a hydropic fetus who died after four weeks of follow-up. Within that period, the left ventricular myocardium had developed extensive echo-dense patterns suggesting tumorous infiltration. Autopsy revealed extreme calcification of the mitral valve, which had mimicked a tumorous mass on fetal echocardiography. The histological results were consistent with viral myocarditis.