The majority of fetal cardiac tumors are primary tumors (1) that usually occur in the heart or pericardial cavities, with rhabdomyoma being the most common tumor type (2). Fetal cardiac tumors are rare, with a global incidence rate of ~0.14% (2). Notably, rhabdomyoma is frequently associated with tuberous sclerosis (2). Heart tumors are 20–30 times more common than pericardial tumors and 75% of primary heart tumors are benign; malignant heart tumors are identified less frequently (3). In 1982, DeVore et al used prenatal ultrasonic examination to diagnose fetal cardiac tumors and to evaluate the function of the fetal heart (4,5). Since then, ultrasonic examination has been widely used for fetal screening, allowing for the majority of fetal cardiac tumors to be detected (6). However, successful resection of such tumors is rare, and literature regarding intraoperative monitoring is limited. On ultrasonic examination, rhabdomyoma generally exhibits a uniform high echo, a myocardial echo which is stronger than normal and tuberous sclerosis may also be present. The identification of multiple tumors is common, and such tumors may cause significant hemodynamic disturbances as a result of outflow obstruction or arrhythmias (7). The occurrence of cardiac tumors may cause numerous types of serious blood disorder in fetuses and neonates and may cause fetal mortality. Thus, it is necessary to dynamically monitor the fetal cardiac hemodynamic change (8) and to continuously evaluate the function of the fetal heart by echocardiography (9,10). Accurate prenatal ultrasonic examination of the fetal heart demonstrates important clinical value for the treatment and clinical decision making of fetal cardiac tumors (11).

Out of the 8 fetuses identified to possess fetal cardiac tumors, 2 fetuses possessed tumors located within one cardiac ventricle and 6 fetuses possessed tumors located in multiple ventricular cavities or ventricular walls. In total, 6 patients requested termination of the pregnancy and the other 2 patients continued with the pregnancy. Out of the 8 fetuses with cardiac tumors, only 2 demonstrated arrhythmia.

All 8 fetuses possessed a hyperechoic or slightly hyperechoic mass, without evident pedicle, and the masses did not move in large amplitude with cardiac contraction and diastole. No significant hemodynamic disorder or induced obstruction of valves was identified (Table I).

In total, 1 patient (No. 4; Table I) continued with the pregnancy and the fetus was followed up during pregnancy and subsequent to birth by cardiac echocardiographic examination (Fig. 1).

One fetus (No. 2; Table I) was found to possess a 10×6 mm oval high echo, with wide basement membrane but without pedicle, in the left ventricular cavity of the fetal heart at the first ultrasonic examination at the gestational age of 21 weeks (Fig. 2A). This pregnancy was continued and a follow-up was performed. At 26 weeks gestation, a check-up was performed and it was found that the hyperechoic mass in the left ventricular cavity of the fetal heart had increased to ~16×10 mm and an additional hyperechoic mass 7×6 mm in size was found in the right ventricular cavity (Fig. 2B). The patient then chose to terminate the pregnancy. Autopsy examination confirmed that the masses were rhabdomyoma (Fig. 2C and D) and there were multiple nodules in each of the fetal kidneys.

Fetal cardiac tumors mostly occur as primary tumors and the incidence rate accounts for 1/10,000 cases of fetal heart disease, among which >90% are benign (1). Rhabdomyoma remains the most common histological type of fetal cardiac tumor at present, accounting for 60% of lesions, followed by teratoma, fibroids and hemangioma (13–16).

As detected using echocardiography, fibroma demonstrates equal echo and teratoma demonstrates an uneven echo, usually in the pericardium, while hemangioma demonstrates low echo nodules, with internal tubular echo, or exhibits rich blood flow signals by Doppler ultrasonic examination (11). Rhabdomyoma generally exhibits uniform high echo, stronger than normal myocardial echo, and are usually multiple space-occupying lesions (17,18). Rhabdomyoma may be combined with tuberous sclerosis (19) or damage to other organs, including brain, kidney and liver damage (6). In the present study, the fetal cardiac tumor in 1 fetus demonstrated an increase in size and number when follow-up was performed, while the nodular shadows in the fetal kidneys did not exhibit any evident abnormal echo. The subsequent autopsy examination identified nodules in the kidneys (20). It has been reported that a small number of rhabdomyoma lesions demonstrate a diminishing trend during the years subsequent to birth, and certain lesions disappear naturally (21). Certain studies have even considered fetal cardiac rhabdomyoma to not be a true tumor, but as a hamartoma (22).

When a small and single occupying lesion is identified in the fetal heart, the patient should receive dynamic observation and close follow up (21). However, systemic examination of the nervous system and organs of the fetus should be performed using magnetic resonance imaging (MRI) to identify any damage to other organs (23). In the present study, 2 patients continued with the pregnancy when occupying lesions in the fetal heart were identified. Follow-up was performed for 1 patient from early gestation, subsequent to the identification of a single and small occupying lesion in the fetus, while the other patient was in late gestation and no more abnormality was identified during the follow-up period. Each of the 2 patients underwent MRI but no other evident pathological change was found. Under these circumstances, the fetus may survive. However, it is reported that the recurrence rate is ≤50% (24) and the prognosis is poor. Thus, pregnancy should be terminated when recurrence is identified (25), as a more serious hemodynamic disorder is also likely to occur in the neonatal period and lead to neonatal mortality or neurological symptoms, or other severe complications (26). Therefore, all patients in the present study were constantly followed up prior to the time of writing.

Ultrasonic examination possesses numerous characteristics, such as non-invasiveness, a lack of radiation, repeatability and high diagnostic rate, which indicates that this examination is the best choice for detecting fetal cardiac space-occupying lesions (10). With the constant improvement of ultrasonographic technology and the improved knowledge of diagnostic ultrasonography, early cardiac tumors may be accurately detected (24). However, this should be differentiated with strong echo spots in the ventricular cavity and certain normal heart structures, such as the small papillary muscle (25). Therefore, it should be dynamically and closely followed up in order to avoid misdiagnosis or missed diagnosis (21). During the follow up period, the observations should be compared with the previous examination, to enable the observation of changes in tumor size and the resulting abnormal heart function or blood stream obstruction. Close and dynamic prenatal follow-up may aid in the reduction of the fatality rate and rapidly allow ultrasonic diagnosis to provide additional important novel clinical information for obstetricians and pediatricians. Therefore, prenatal ultrasonic diagnosis of space-occupying lesions in the fetal heart possesses considerable clinical value and is conducive to a healthy birth and good care in developing countries.