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Malignant melanoma has a very high tendency to metastasize to the heart. Although most cardiac metastases of melanomas are clinically silent, the lesions may present with life-threatening cardiac morbidities, including dysrhythmia, right ventricular outflow tract obstruction, myocardial dysfunction, pericardial effusion, or heart failure. In selected patients who have a solitary intracardiac melanoma, surgical resection can provide relief from clinical symptoms and minimize potential cardiac sequelae of the tumor. Because tumor embolization of cardiac melanoma has been reported, the presence of atrial metastatic melanoma can be another indication for surgery.
Herein, we present the case of a 31-year-old man who had a right atrial metastatic melanoma of unknown primary origin. He underwent surgical resection of the tumor before beginning a course of chemotherapy. After 1 year, he was well and had no symptoms. We describe the clinical features of this rare presentation of melanoma.
Malignant melanoma can be metastatic and can carry a high tendency for cardiac involvement. In an autopsy series of 70 patients with metastatic melanoma, cardiac metastasis had occurred in 64% of the cases.1 Although the heart is generally involved as a part of disseminated disease, it has been reported that an intracardiac melanoma was evident in less than 2% of living patients.2,3 Patients have survived in the short term after the resection of isolated intracardiac melanomas, but there has been no collective experience to suggest that this treatment influences longer-term survival. Nonetheless, the complete resection of a solitary intracardiac melanoma can relieve cardiac symptoms and prevent associated morbidities. Herein, we present the case of a patient who underwent complete resection of a solitary metastatic melanoma of the heart, and we discuss the clinical and pathologic features of this rare presentation.
In July 2008, a 31-year-old man was admitted to the hospital with heartburn and dyspepsia. He had experienced no weakness, weight loss, or loss of appetite within the last 6 months. His medical history included no previous cardiac disease. A physical examination revealed no cardiac or abdominal abnormalities. However, a 1 × 1.5-cm lymphadenomegaly was incidentally discovered in the left subclavian area. A pathologic evaluation of this lesion resulted in a diagnosis of malignant melanoma even though dermatologic inspection had revealed no skin lesion, dysplastic nevus, or suspicious pigmentation. Laboratory tests produced values that were within normal ranges. Abdominal ultrasonography showed an irregular hyperechogenic mass in the gall bladder that suggested another metastatic lesion as the cause of the patient's dyspepsia. The diagnosis was metastatic melanoma of unknown primary origin.
The origin and systemic dissemination of the melanoma were investigated. A fluorodeoxyglucose positron emission tomographic (PET) scan revealed a hypermetabolic mass in the patient's right atrium. A transthoracic echocardiogram confirmed the presence of a single 17 × 21-mm hyperechogenic lesion in the right atrium (Fig. 1). The orifices of the superior and inferior venae cavae were open, and no tricuspid valvular or atrial septal dysfunction was evident. A computed tomographic scan of the chest did not show an associated pulmonary disorder. The hospital's oncology clinic planned a course of chemotherapy for the patient; however, in order to avoid potential cardiac morbidities, surgical excision of the right atrial lesion was recommended before the start of medical therapy.
In our clinic, the patient was placed under cardiopulmonary bypass for an open cardiac procedure with bicaval venous cannulation. Before atriotomy and exposure of the lesion, manipulation of the right atrium and the tumor was avoided because of the risk of iatrogenic tumor embolization. When the right atrium was opened and exposed with stay sutures, an isolated, black intra-atrial mass was seen firmly adhering to the lateral wall (Fig. 2). The endocardium, pericardial space, and orifices of the venae cavae and coronary ostium were all free from tumor involvement. The tumor was completely resected along with tissue of the right atrial wall that was connected to its base, and the wall defect was repaired.
Pathologic examination revealed a 2.9 × 2.5 × 1.8-cm tumor that weighed 5.7 g. The tumor was lobulated, black in color, and soft. The lesion had a 0.8 × 0.6-cm reddish base over the right atrial wall (Fig. 3). Microscopic examination of the mass showed that the tumor extended through the endocardium and was attached to, but did not invade, the myocardium (Fig. 4A). Diagnosis of an epitheloid type of malignant melanoma was determined from the presence of atypical melanocytes and dense intracytoplasmic melanin pigment (Fig. 4B).
The patient's postoperative course was uneventful. He was discharged from the hospital on the 6th postoperative day and was referred for chemotherapy. At 1-year follow-up, he was well with no evident tumor recurrence in the heart or gall bladder.
Malignant melanoma is a neoplasm that develops after the malignant transformation of melanocytes of the skin, mucous membranes, upper esophagus, anus, eyes, or meninges. The skin is the most common location of a primary lesion. Family history, genetic causes, dysplastic nevi, skin type and pigmentation, and sun exposure can influence the development of melanoma. Cardiac and pericardial metastases, which are much more common than are primary cardiac tumors, are usually associated with a poor prognosis. Despite inherent challenges in the clinical diagnosis of cardiac melanoma, early detection has important therapeutic and prognostic implications.
Of metastatic cancers, melanoma has the highest frequency of metastasis to the heart.1 Most such metastasis occurs after multifocal hematologic dissemination3 and may occur anywhere in the heart. Melanotic metastases can invade the walls of all 4 cardiac chambers, and the right atrium is involved most frequently.1,4 Cardiac metastases typically involve the pericardium and myocardium; the endocardial layer is rarely involved. In addition, metastatic melanoma of the pericardium and myocardium usually presents with multifocal lesions. However, solitary melanoma in a cardiac chamber is a rare presentation and is chiefly an anecdotal finding of metastatic melanoma.
Patients with malignant melanoma can have cardiac metastases but present with symptoms caused by tumors in other organ systems.2 Cardiac involvement occurs during the course of the disease, but only rarely is cardiac metastasis the initial manifestation. Although the initial definitive antemortem diagnosis of metastatic melanoma of the heart is rare, suspicious symptoms include otherwise-unexplained fever, heart murmurs, dysrhythmia, pericardial effusion, or heart failure. Transthoracic or transesophageal echocardiography can be helpful in the diagnosis of the tumor. Computed tomography or magnetic resonance imaging may provide useful information, and PET is a noninvasive imaging technique that is being used to detect occult or distant metastasis at a relatively early stage and to clarify abnormal radiologic findings. In the detection of metastatic melanoma, the overall sensitivity and specificity of PET is higher than that of computed tomography.5
Antemortem histologic confirmation of a cardiac melanoma is challenging but feasible in regard to right-chamber tumors: a percutaneous biopsy may enable identification of the type of tumor and guide appropriate treatment.4 In contrast, the risks of a percutaneous biopsy of left-sided cardiac tumors outweigh the benefits, and exact diagnosis requires an excisional biopsy through an open cardiac procedure.
The medical management of patients who have metastatic melanoma includes palliation of symptoms, and systemic therapy with cytotoxic drugs, biotherapy, or immunotherapy. Long-term survival in these patients is associated with a complete response to systemic treatment; however, there is currently no standard approach to treating cardiac metastases of melanoma. Abnormal vasculature in large tumorous masses creates a diffusion gradient that impairs the efficacy of systemically administered chemotherapeutic agents.6 Therefore, resecting a visible intracardiac tumor may be an effective palliative measure in selected patients in whom the heart is the chief site of disease, and resection may augment the effectiveness of adjuvant therapies.
A tumor's anatomic location and extent of invasion determine the feasibility of surgical intervention, which should optimally be performed during the early stages of the disease. Completely resecting an intracardiac melanoma prevents potential morbidities that are associated with progressive intracardiac growth, such as superior vena cava syndrome, right ventricular outflow and inflow obstruction, dysrhythmia, cardiac tamponade, and heart failure.7,8 Systemic tumor embolization of metastatic cardiac melanoma has been reported,9–11 and resecting an asymptomatic mass can therefore avert an impending cardiac catastrophe. Resection reduces the risk of pulmonary embolization of a right atrial tumor. Even when total resection is not possible, conservative surgery can relieve symptoms and prevent imminent cardiac failure. Resection improves the quality of a patient's life,12 as in our patient's case.
To reduce the risk of tumor embolization during surgery, the tumor and the heart should be manipulated as little as possible. Bicaval venous cannulation or the use of femoral veins reduces the risk of procedure-related morbidities.12 Our pathologic findings showed that effective surgical resection required exclusion of the invaded atrial wall and not just blunt dissection of the tumor itself (Fig. 4A). In some cases, augmenting the atrial wall with autologous pericardium is necessary after tumor resection to prevent narrowing of the inferior or superior vena cava.12,13
In conclusion, metastatic cardiac tumors are rarely encountered by cardiac surgeons. In symptomatic patients, the resection of a metastatic cardiac melanoma can relieve the associated symptoms—and, in asymptomatic patients, prevent intracardiac sequelae. The case of our patient shows that surgical resection is safe and feasible in selected cases of solitary metastatic melanoma and that effective resection requires the extended removal of a tumor that involves the atrial wall.
Address for reprints: Burak Onan, MD, Feneryolu Mahallesi, Fenerli Ahmet Sokak, Ugur Apartmani, No: 36, A-Blok, Da:2, 34730 Kadikoy, Istanbul, Turkey