- An uncommon but important differential diagnosis of cardiac masses.
- Diagnosis is suspected by history, physical examination, and imaging characteristics and confirmed by biopsy of mass.
Cardiac tumors arise either as a primary tumor of the heart or more commonly from metastasis of a distant noncardiac primary tumor. Because of the low incidence and nonspecific clinical manifestations, cardiac tumors have often been diagnosed incidentally during evaluation of a seemingly unrelated problem or misdiagnosed as other cardiac conditions. A high index of suspicion in combination with characteristic cardiovascular imaging study is essential for rapid identification of cardiac tumors.
Metastatic Cardiac Tumors
Metastatic cardiac tumors are a 100-fold more common than primary tumors. Cardiac metastases often present as pericardial effusions; myocardial, coronary, and intracavitary involvement occur uncommonly, in order of decreasing frequency. The tumor that has the highest predilection for metastasis to the heart is disseminated malignant melanoma, which occurs in 50–65% of afflicted patients (Figure 32–1). The common noncardiac sources of metastatic cardiac neoplasms are neoplasm of the lungs, hematopoietic (lymphoma and leukemia) and gastrointestinal cancers (esophageal and liver), breast cancer, and renal cell carcinoma. Cancers from the respiratory system have been consistently shown to be the most common source of cardiac metastasis in different series; the relative proportion of other primary noncardiac malignancy for cardiac metastasis varies according to the local cancer incidence.
Magnetic resonance imaging of the heart in a 50-year-old man who presented with dyspnea on exertion, 3 months after a diagnosis of melanoma on his back was made. A large pericardial mass was demonstrated on (A) bright blood-cine steady-state free precession image in axial plane. The arrows show the extension of the mass into the pleural space and possibly lung parenchyma. The asterisk indicates different texture of the myocardial signal, suggesting myocardial invasion of the mass. (B) Coronal black-blood T1-weighted image showing extension of the mass anteriorly and superiorly to impinge on the proximal left anterior descending artery (arrow head). Biopsy of the mass confirmed metastatic melanoma. AO, aorta; LV, left ventricle; MPA, main pulmonary artery; RA, right atrium; RV, right ventricle. (Courtesy of Karen Ordovas).
Malignant cells from any single source can metastasize to the heart via multiple routes and can often seed in multiple cardiac structures. For example, adenocarcinoma of the colon can metastasize to the heart by lymphatic or hematogenous spread, usually affecting first the pericardium and then the myocardium. Cardiac metastases that occur in patients with colon cancer are usually preceded by involvement of other organs. Metastases to the endocardium have been reported in renal cell carcinoma, which can also extend into the inferior vena cava, and the tumor thrombus occasionally involves the right atrium (Figure 32–2).