Discussion
Carcinoid tumors are slow-growing, low-grade malignancies derived from neuroendocrine cells. Carcinoid tumors can be invasive and can metastasize to lymph nodes and the liver. However, carcinoid tumors usually have good prognosis because they are generally well differentiated and grow slowly. Over 70% of carcinoid tumors arise along the digestive tract and are infrequently found in mediastinum.1 Mediastinal carcinoid tumors usually derive from thymic enterochromaffin-like cells or ectopic growth of bronchial mucosal argyrophilic cells during foregut embryonic development. Mediastinal carcinoid tumors are often seen around the major blood vessels and pericardium at the base of the heart. They can grow along the vascular space and compress and invade large blood vessels and pericardium.
The incidence of cardiac tumors is low. The modes of carcinoid tumors metastasis include direct diffusion, lymphatic metastasis and hematogenous metastasis 2. In this case, the coronary vessels, located in the epicardium or superficial myocardium underneath the epicardium, branch towards the heart wall at right-angle, invade the myocardium from the epicardium and then invade the endocardium. Regarding cardiac metastases, pericardium metastasis has the highest incidence, about 90%, while cardiac chamber and myocardium metastases occur in about 10% cases. About 7% patients with cardiac metastases will have signs and symptoms of heart dysfunction.3 In this report, the patient had reduced LV systolic function, with EF of 44%. About 11–60% carcinoid patients have carcinoid heart disease,4 which typically causes valve and endocardium diseases leading to right ventricular failure. The common symptoms include tricuspid and pulmonary valve regurgitation or stenosis and they mainly occur in late-stage carcinoid patients with liver metastasis. In 74 patients with carcinoid heart disease, three had cardiac metastasis.5 The patient in this report did not have valve involvement, but had masses within the LV, myocardium, and epicardium. Moreover, the mass within the LV swung slightly. Once tumor tissues shed, they may cause infarction in vital organs, which might be life threatening.6 The patient decided surgically removed the mass at last.