DISCUSSION
Although primary tumor of the heart is rare with the reported prevalence of 0.1%-0.01, metastatic cardiac tumor is more frequent than primary tumors with the range of 0.7%-3.5% in autopsy series.1 The prevalence of cardiac metastasis is reported up to 9.1% in oncology patients. The leading malignancies that metastasize to heart are lung, breast and hematologic malignancies with the rates of 36-39%, 10-12% and 10-21%, respectively.1 Prostate cancer is the most common malignancy in men, but nevertheless hardly metastasize to heart due to its low aggressiveness.2
The common mechanism of lung cancer to metastasize to the heart is by means of direct extension to epicardium or pericardium.2 Other possible pathways for various malignancies are lymphatic (most common) and hematogenous spread. Renal cell carcinoma is the leading cause for transvenous (caval) extension. Yet, lung cancer tends to use pulmonary veins to reach left atrium.3 Myocardial metastasis is rare and endocardial or intracavitary metastases are even rarer. The right chambers are affected mostly up to 80% and right atrium is the common site for metastases.4
Due to most cardiac metastases are indolent and course without cardiac specific symptoms, the diagnose often delay untill the advanced stages of the disease even at autopsy if not detected incidentally by imaging.1 If any symptom occurs, location and size of the tumor or invasion to surrounding organs may determine the clinical scenario. The involved chambers or valves may be obstructed, coronary flow may be altered due to mass effect, contraction abnormalities or arrhythmic interferences may occur5. Direct invasion of the tumor can result malignant pericardial effusion.
Echocardiography is the first line imaging modality to detect any obvious masses in any chambers, valves or apparent myocardial thickening.5,6 Transesophageal echocardiography (TEE) is superior than any other imaging modalities to reveal valvular mass lesions and its hemodynamical consequences.5 Computed tomography (CT) and cardiac magnetic resonance (CMR) are useful tools to detect, localize and characterize the mass. CMR has the unique feature to reveal tissue characteristics which is of utmost importance in case of any myocardial mass.6 Contrast administration may aid in differentiating between thrombus and tumor.6
In conclusion, though cardiac metastases in lung cancer patients are expressed at the late stages of the disease, it is vital to detect any metastasis to adequately manage the patients as survival rate prolongs with the aid of novel therapies. Patients with known malignancy necessitates clinicians, echographers or imagers being more vigilant in case of unexpected myocardial thickening as it might resemble hypertrophic cardiomyopathy phenotype.