Cardiac tumours are infrequent clinical entities both in adult and paediatric age groups; they can be divided into primary and secondary; approximately 75% of primary cardiac tumours are benign, and 25% are malignant . The occurrence of metastatic cardiac tumours has been reported 100-fold more commonly than primary lesions. Approximately half of benign cardiac tumours in adults are myxomas, and the rest are lipomas, papillary fibroelastomas, and rhabdomyomas. Among malignant primary cardiac tumours, the most reported are those histopathologically considered as undifferentiated, followed by angiosarcomas and leiomyosarcomas.
Cardiac tumours in children are rare. It is difficult to estimate the real prevalence because the available data are restricted to autopsy and case records from leading paediatric centres. It is believed that they constitute less than 0.1% of all neoplasms and occur with an incidence of 0.0017 to 0.28 in autopsy records [5, 6].
Among 27.640 patients examined echocardiographically in 5-year periods, the incidence of cardiac tumours increased: 0.06% (1980–1984), 0.22% (1985–1989) and 0.32% (1990–1995) of all the subjects .
Benign lesions usually predominate, making up more than 90% of all paediatric tumours: rhabdomyomas are the most frequent cardiac tumours in children (45-50%), followed by fibromas (25-30%), mixomas, lipomas, teratomas, hemangiomas, etc. [8–10]. The most common malignant primary tumours are angiosarcoma, fibrosarcoma, lymphosarcoma, and giant cell sarcoma . Secondary cardiac neoplasms in the paediatric population include non-Hodgkin lymphoma, leukemic infiltration, and neuroblastoma.
Rhabdomyoma is the most common cardiac tumour in paediatric patients. It usually presents during the first few days after birth, but it can be diagnosed in the third trimester of pregnancy.
Foetal cardiac rhabdomyoma accounts for less than 10% of foetal demise cases . Cardiac rhabdomyomas are benign from the cardiovascular standpoint in most affected foetuses. They are associated strongly with tuberous sclerosis, a hereditary disorder characterized by hamartomas in various organs, epilepsy, mental deficiency, and sebaceous adenomas . Rhabdomyoma (especially multiple) affects about 50% of children suffering from tuberous sclerosis, but more than 50% of patients with rhabdomyoma have or will develop tuberous sclerosis. The exceptional patient is one with a solitary, single rhabdomyoma who does not have or develop tuberous sclerosis.
Over 90% of rhabdomyomas are multiple and occur with approximately equal frequency in both ventricles. The atrium is involved in fewer than 30% of patients.
Macroscopically, these tumours are firm, grey, and nodular and tend to project into the ventricular cavity. Microscopy shows myocytes of twice normal size filled with glycogen and containing hyperchromatic nuclei and eosinophilic-staining cytoplasmic granules. Scattered bundles of myofibrils can be seen within cells by electron microscopy.
These tumours grow during the second half of pregnancy; they have the tendency to diminish or even completely disappear spontaneously after birth. Many will disappear entirely; alternatively, the tumour size remains constant as the heart grows, which has much the same effect [13, 14].
In the majority of cases cardiac rhabdomyomas are clinically completely silent and have a benign course. They may be incidentally discovered during an echocardiogram, but they also may cause cardiac dysfunctions requiring medical and/or surgical intervention. During foetal life and the early neonatal period, life-threatening conditions, mostly due to arrhythmias, cardiac failure or obstruction, do occur on rare occasions . How threatening rhabdomyomas are, in terms of clinical presentation and presence of hemodynamic complications, depends on their size, location and number of lesions. Although the behaviour of cardiac rhabdomyoma is benign, its positioning within critical areas in the heart can lead to lethal arrhythmias and chamber obstruction. The most common presentation is heart failure caused by tumour obstruction of cardiac chambers or valvular orifice flow. Clinical findings may mimic valvular or subvalvular stenosis. Arrhythmias, particularly ventricular tachycardia and sudden death, may be a presenting symptom [16, 17]. Atrial tumours may produce atrial arrhythmias. The mechanism of their causing sudden death is likely rhythm disturbances, particularly the Wolff-Parkinson-White ventricular pre-excitation syndrome . The conduction abnormalities and the arrhythmia are thought to be due to the tumoral mass, which may lead to degeneration of the cardiac conduction system and compose a substrate for re-entrant arrhythmia, e.g. the development of atrioventricular block and ventricular arrhythmia. Large tumoral mass in the myocardial region, accompanied with arrhythmia, revealed that the neoplastic mass could affected the common bundle of His, in addition to the ordinary myocardium, being causative of circulatory failure [18, 19].
Although most cardiac rhabdomyomas have a relatively benign perinatal course, the long-term prognosis is determined by the neurological manifestations associated with tuberous sclerosis.
Rhabdomyoma may be detected prenatally by ultrasound in the third trimester of pregnancy. However, a large number is diagnosed in infancy. The diagnosis is suggested by clinical features of tuberous sclerosis and is made by echocardiography. Heart echocardiography, CT and MRI are the major non-invasive diagnostic procedures, while angiography is used in selected cases, due to its invasive nature. Even though ECG is not specific for the diagnosis, it is important to establish the presence of rhythm disorders, while a chest X-ray may show an enlarged heart silhouette or abnormal cardiac contours.
Therapeutic strategies should be individualised: the total resection is not the only therapeutic aim, in fact, the restoration of the regular heart function may be of primary relevance. Antiarrhythmic agents successfully control the clinical and electrophysiological conditions, while surgery is indicated in children with significant clinical symptoms. Benign cardiac tumours in childhood have an excellent prognosis when completely excised and have a good short-term prognosis even when excision is incomplete. Asymptomatic patients require anyway a close follow-up .
This report outlines the importance of an early diagnosis of cardiac tumours: when the prenatal and/or neonatal diagnosis of rhabdomyoma is made, an appropriate planning and an accurate follow-up may be performed to formulate individualised therapeutic strategies, improving in this way the clinical outcome and, eventually, anticipating the development of tuberous sclerosis.