BACKGROUND

With an incidence of 0.02% in a pooled autopsy series, primary tumours of the heart are far less common than secondary or metastatic cardiac tumours. Approximately three-quarters are histologically benign. The occurrence of secondary tumours are approximately 100-fold more frequent than primary cardiac tumors.1^,2

Hamartoma have been described most commonly in the left ventricle;3 other sites include the septum, right ventricle, all four heart valves,4 most commonly the mitral valve5 and the atrium.6^–8

Although many tumours are histological benign, all cardiac tumours are potentially lethal as a result of intracavitary or valvular obstruction, peripheral embolisation, disturbances of rhythm or conduction and alteration of normal myocardial contractility.9^–12 Unfortunately, it is usual for patients to die or experience a major complication while awaiting operation and, therefore, it is mandatory to carry out the operation promptly after diagnosis has been established.

In previously reported cases, hamartoma located in the right atrium had no apparent cardiac symptoms. The present patient noticed palpitation and chest distress with the inflammatory syndrome.

In regard to clinical evolution, the patient may be asymptomatic and the diagnosis established as a surgical or complementary examination finding. One of the most important problems with cystic hamartoma is the potential risk of a patient with no previous cardiac history suddenly lapsing into a critical condition necessitating rapid diagnostic and therapeutic measures for survival, and the possibility of other malignant cardiac tumours. In our opinion, surgical resection should be carried out.

In our patient, the cystic hamartoma was 10×9 cm in size and in relation to the right atrial free wall and presented as a mass compressing the right atrium, which was mistakenly thought to be a pericardial tumour.

CASE PRESENTATION

An 11-year-old boy with no cardiac history was transferred to our university hospital from another hospital because of repeated chest distress and chest pain. He had a history of fever of about 38.5°C. His body weight was 31 kg and his height was 152 cm. On his initial examination at the referring hospital, his pulse was 102 beats per minute and he had normal blood pressure at 99/75 mmHg with a normal respiratory rate. He had engorged jugular vein and his neck veins were elevated to the angle of his jaw at 45 degrees. The remainder of his physical examination was unremarkable.

Laboratory examination demonstrated an increase in C-reactive protein (64.90 mg/dl), creatinkinase-isoenzyme (40.8 U/L), lactate dehydrogenase (266.5 U/L) and haematological tests were within normal limits. Serological tests for parasites, including Echinococcus, blood fluke, hydatid, lung fluke, bladder worm and pleroceroid, and tumour markers (including B-human gonadotropin) were negative.

Chest radiography revealed marked enlargement of the heart with a bulge from the right atrium and no evidence of metastatic nodules in the lung fields. The electrocardiogram showed left axis deviation of 330, an incomplete right bundle branch block and T wave changes in lends II, III and aVF. Transthoracic echocardiogram (apical four-champer view) revealed a slight to moderate pericardial effusion and a cystic mass measuring 90×91 mm² in size causing compression of the whole regions of the right atrium and deviation of the cardiac structures to the left. No communication between the mass and atrial lumen was detected by colour echo-Doppler (fig 1A). An enhanced CT scan showed a large cystic structure in the pericardial cavity and slight pleural effusions in the right thoracic cavity (fig 1B).

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Figure 1

(A) Transthoracic echocardiography displayed a right atrium mass of approximately 9 cm and caused compression of the whole regions of the right atrium and deviation of the cardiac structures to the left. RA, right atrium; RV, right ventricle. (B) Contrast-enhanced CT scan showing a large cystic structure in the right atrium.

DIFFERENTIAL DIAGNOSIS

Clinically and pathologically, cystic hamartoma of mature cardiac myocytes differs from cardiac rhabdomyoma, cardiac fibroma and pericardial cysts such as mesothelial cysts and cystic lymphangiomas. Cardiac rhabdomyoma is exceptionally rare after the age of 10 years and is strongly associated with tuberous sclerosis.13^–15 It is also composed of immature cardiac myocytes with diffusely vacuolated myocytes and extensive glycogen deposits, whereas the myocytes in hamartoma are hypertrophied and display only focal areas of vacuolisation. There is a tendency for these lesions to spontaneously regress during the first year of life.16 Cardiac fibroma is also primarily found in children17^,18 and is a mass of fibrous and elastic tissue formed predominantly of collagen and fibroblasts.19 Fibroma is generally poorly vascularised and focally calcified, whereas hamartoma of mature cardiac muscle is non-calcific and may be highly vascularised with dilated venous channels.20 Mesothelial cysts originate in the atrioventricular node region and have a broad connection with the interatrial septum and no stalk.21^,22 Histologically, the cystic walls are composed of fibrous connective tissue covered by a layer of squamous or cuboidal epithelium. On gross examination, cardiac lymphangiomas may be either soft and spongy or firm and fibrous. The tumours are composed of capillaries or lymphatic vessel with clear to milky content. Histology from the cyst wall demonstrates endothelial lining and small lymphoid aggregates.23

The pericardial cysts wall shows fibrous connective tissue with scattered elastic fibres lined by a single layer of flat cells similar to serosal and endothelial.24 Foci of hyperplastic mesothelial cells, calcification and plasma cells or lymphocytes may be encountered.25

From all of the above, in the present case the cystic mass was filled with the chemical characteristics of transudate. Anatomopathological examination showed an irregular distribution of histological elements, including disordered, hypertrophied myocytes, surrounded by interstitial fibrosis, dilated venule and thick-walled arteries. Therefore, the current case is not consistent with the reported case but instead is best described as a giant intramural atrial cystic hamartoma with infectious process.

TREATMENT

According to the ultrasonic cardiography and enhanced CT scan findings, the mass exhibited cystic characteristics. A cardiac cyst was considered, but the aetiology of the cyst was still unknown. Pericardial cysts, intramural right atrium cysts, right atrium myxoma, bronchogenic cysts, teratogenic cysts, mesothelial cysts, cystic lymphangiomas and metastatic tumour were suspected in the differential diagnosis. The risk of complications from cyst rupture, such as haemopericardium causing acute cardiac tamponade, would have devastating consequences even if the aetiology of the mass was benign. We, therefore, decided to remove the mass surgically.

A median sternotomy was performed. After opening the pericardium, approximately 80 ml of bloody fluid was aspirated from the pericardial cavity. The cyst found to be located in the whole right atrium wall was large and had a well-developed capsule. It was a 100×100 mm² blood-containing cyst and attached to the atrioventricular groove and the right coronary artery. The basilar part of the cyst was located in the right atrium free wall. The wall of the cyst was thin and non-contractile, but no ruptured was found. Partial cystotomy was performed on the anterolateral wall, which provided access to a large cavity filled with haematological material (fig 2).

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Figure 2

Appearance of the right atrial wall after partial cystotomy.

OUTCOME AND FOLLOW-UP

The cystic mass consisted of the capsule, bloody fluid and atrial myocardium. Normal atrial myocardium and right coronary artery were found to be located in the basilar part of the cyst. Histological examination showed that the cyst wall consisted of fibroplasia with focal hyalinosia. Lymphangiectasia and lymphoid infiltrates were found in the right atrial myocardium. Immunohistochemical examination showed a positive reaction for CR, CK, CD₃, CD₂₀ CD₆₈ and CD₃₄ (fig 3A–D).

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Figure 3

Microscopic features of hamartomas in surgical tissue. (A–C) Myocyte disorganisation and focal pericellular interstitial haemorrhage, oedema and fibrosis, myocyte hypertrophy, interstitial fibrosis, thickened intramural coronary arteries and dilated venule were present, chronic inflammatory cell dispersed infiltration (H&E stain: A and B ×100; C ×200). (D) Abundant fibrous connective tissue and malformed blood vessels (CD₃₄ positive) (D ×100 SP).

The laboratory examination of the fluid from the cyst showed massive red blood count, and white blood cell and biochemistry showed total protein 55.6 g/L, albumin 33.7 g/L, globulin 18.3 g/L, glucose 3.08mmol/L and chlorine 110.7mmol/L.

No evidence of malignancy was found. The pathological diagnosis confirmed a giant right atrial cystic hamartoma with infectious process. The postoperative course was uneventful and the patient was discharged from hospital on the 7th postoperative day.

The patient had no symptoms or recurrence by transthoracic echocardiogram studies 3 months post-partial resection.

DISCUSSION

Hamartoma are one of the rarest types of benign cardiac tumours. Tanimura et al first described hamartoma composed of mature heart cells in 198826 and only a small series has been reported in the literature. To our knowledge, hamartomas of mature cardiac myocytes have been reported in only 16 patients.3^,6^–8^,20^,27^–29 Other benign cardiac tumours, in order of frequency, include myxoma, fibroma, rhabdomyomas and lipomas. Although the origin of hamartoma is controversial, it is a benign overgrowth of the mature, differentiated and disorganised cells of the organ in which it is found. The mass results from the anomalous development of embryonic cells that are typically native to the affected organ.30

An essential characteristic of cardiac hamartoma is the presence of hypertrophied myocytes lying in a disorderly fashion and mixed with dilated venules, thick-walled arteries, interstitial fibrosis and adiposity in different proportions in patients.3^,6^–8^,20^,27^–29

To date, only five cases of atrial mature cardiac myocyte hamartoma, including the present case, have been reported in the literature.6^–8 Burke et al6 reviewed a 28-year-old patient with a history of Wolff-Parkinson-White syndrome and an episode of syncope, and a 9-year-old boy who died suddenly and unexpectedly. Echocardiography showed a mural mass in the right atrium in the first patient. On post-mortem examination, the younger patient’s heart had multiple nodules scattered throughout the heart, including the atrial wall. Chu et al7 describe an unusual cardiac hamartoma originating from the crista terminalis and extending towards the tricuspid valve in a 76-year-old man with mild systolic hypertension that was well-controlled by atenolol for 10 years. Movahedi et al8 reviewed a 58-year-old man who underwent coronary artery bypass grafting surgery during which a hamartoma in the right atrium was discovered. In our patient, hamartoma located in the front wall of right atrium and extending to the atrioventricular groove was found. Unlike the previously reported cases, the morphological appearance of the lesion in our case was a cystic giant hamartoma complicated by an infectious process.

Echocardiography, electrocardiography, enhanced CT imaging and MRI have been helpful not only in detection and diagnosis but also in providing information that can assist surgical treatment.

In the excision of pericardial tumours, which are commonly found over the right atrium and may extend to the ventricles, particular attention must be paid to the preservation of the coronary arteries. An attempt at removal of an extensive tumour must be tempered by the possibility of irreparable injury to the coronary arteries. The clinical presentation of cardiac hamartoma, similar to other localised cardiac masses, varies according to location in the heart. One of the most common manifestations of these tumours is ventricular tachycardia in children and young people.27^,31^–33 In previously reported cases, hamartoma located in the right atrium had no apparent cardiac symptoms. The present patient noticed palpitation and chest distress with the inflammatory syndrome.

In our case, based on the histological findings, inflammatory processes may have played an important role in the development of the cyst because infiltration of inflammatory cells was apparent in the cyst wall. Additionally, total obstruction of the proximal right coronary artery suggested that possible ischaemia and/or infarction in the right atrium might be correlated with the formation of the cyst.34 An ischaemia-related lesion was detected as the serum creatine kinase isoenzyme level increased. In regard to clinical evolution, the patient may be asymptomatic and the diagnosis established as a surgical or complementary examination finding. One of the most important problems with cystic hamartoma is the potential risk of a patient with no previous cardiac history suddenly lapsing into a critical condition necessitating rapid diagnostic and therapeutic measures for survival, and the possibility of other malignant cardiac tumours.