Echocardiographic diagnosis of an unusual anterior mediastinal mass.

X-ray chest and CAT scan suggested an anterior mediastinal mass in a girl who had prominent left parasternal pulsations. M-mode and two dimensional echocardiography demonstrated an extracardiac fairly rigid cystic mass between right ventricle and chest wall, which proved to be a cystic chondroma arising from the fourth left costal cartilage.