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.