The heart can be involved by primary as well as metastatic tumors. Primary tumors of the heart are rare (< 0.3 % in postmortem series), with myxoma the most frequent. Metastases from neoplasms arising in other organs are far more common and include carcinomas, sarcomas, hematologic malignancies and melanoma. Nonetheless, cardiac metastases are infrequent. Why is the heart relatively protected from metastasis? Possible explanations include the continuous forceful stroke of the heart, rapid blood flow and afferent lymphatic circulation. If these hypotheses were true, cardiac tumors would be present almost invariably in patients with previous cardiac damage with reduced pump action and blood flow, but there is no such confirmatory data in the literature. Regarding afferent lymphatics, metastatic dissemination in the heart occurs most commonly through lymphatic invasion. Overall, the heart is probably protected as a result of the combination of all these and other unknown factors. Moreover, tumor type, metabolic properties of the heart, and adhesion molecules among others, are under consideration and require further investigation.
Secondary tumors may involve the heart by direct extension, hematogenous spread or lymphatic dissemination. Direct extension occurs from tumors arising in the lungs or mediastinum (i.e. bronchogenic and esophageal carcinoma, malignant thymoma, thymic carcinoma). Hematogenous spread is often seen with sarcomas (e.g. uterine. leiomyosarcomas can reach the heart through the inferior vena cava), leukemia, multiple myeloma, and with certain types of carcinoma (e.g. hepatocellular carcinoma). However, the lymphatic pathway appears to be the most significant. This is demonstrated by the frequent metastatic involvement of the pericardium, richly supplied by lymphatic channels that drain in the anterior and posterior mediastinum. In the present case, the patient had a history of adenocarcinoma of the lung involving mediastinal lymph nodes; therefore, it is not surprising that she presented with a pericardial effusion and associated cardiac tamponade. Pericardial involvement in a patient with a known primary malignancy, should be suspected in the setting of pericardial effusion, intractable heart failure or hepatomegaly in the absence of metastatic lesions. The differential diagnosis includes congestive heart failure in a patient with a cardiomyopathy, and non-malignant pericardial effusions (infectious and non-infectious). This patient was young, with no history of heart disease. Although she had asthma in the past and evidence of chronic obstructive pulmonary disease as per the autopsy exam, she did not have pulmonary hypertension or cor-pulmonale.
Tuberculous (TB) pericarditis is a consideration based on her prior history of PPD positivity and antituberculous treatment. TB pericarditis may develop insidiously, or acutely with a large effusion and cardiac tamponade, particularly in immunosuppressed patients. She was HIV negative and had not been treated with chemotherapeutic agents. If she had lived, the diagnosis of malignant pericardial effusion could have been made with a pericardiocentesis and cytologic examination of the fluid. Adenocarcinoma cells are readily identified in pericardial fluid by their tri-dimensional arrangement, distinct cell borders, high nuclear-cytoplasmic ratio and prominent nucleoli (Figure 60). They must be differentiated from reactive mesothelial cells, which is not often easy. Reactive mesothelial cells, especially in long-standing effusions can also exhibit a glandular arrangement, prominent nucleoli, mitotic figures and even vacuolization that mimic adenocarcinoma. Immunohistochemistry is useful in distinguishing the two. Both cell types are immunoreactive to cytokeratin, but only adenocarcinoma stains with the adenocarcinoma marker B72.3 and carcinoembryonic antigen (CEA).
Pulmonary adenocarcinoma arises preferentially in the periphery of the lung parenchyma. Central lesions may occur, but are less frequent. This type of tumor can develop in smokers as well as in non-smokers, de novo or in areas of pre-existing scarring. Our patient was a smoker for 20 years. Although she had a risk factor for lung cancer, the aggressive behavior of this tumor (stage T2, N2 at initial diagnosis) suggests a genetic predisposition.
The advent of cardiovascular imaging studies has improved the diagnosis of cardiac involvement by metastatic disease, but the prognosis remains poor. In a recent study done at the Tottori University School of Medicine in Japan, 46 of 161 patients had secondary cardiac tumors diagnosed by echocardiography. The most common primary site was the lung followed by mediastinum, liver, uterus and testis. Forty seven percent of the cases had pericardial involvement, 32% involved the right side of the heart and 14 % involved the left. Metastases on both sides of the heart were noted in 7% of cases. It is unknown why intracavitary lesions are less common, but there is evidence that certain tumors have predilection for this pattern of growth (Figures 61 and 62). In our experience, squamous carcinoma arising in different sites has the tendency to invade and seed cardiac valves, endocardium and myocardium. Prior valve damage or endothelial damage appears to be a sine qua non in such cases. As a result, death can occur due to arrhythmia with or without conduction system involvement and embolization. Changes in the electrocardiogram such as prolonged elevation of the ST segment are indicative of myocardial invasion.
In the present case, the patient died of cardiac tamponade due to a malignant pericardial effusion. In addition, she was in a hypercoagulable state with numerous acute and organizing pulmonary emboli leading to areas of hemorrhagic infarction. Her symptoms of dyspnea and shortness of breath were related to both the pulmonary embolism and evolving cardiac tamponade. Of note, dyspnea is the most common manifestation of cardiac tumors in general, and is suggestive of cardiac decompensation. Treatment is palliative, aimed at controlling effusions, arrhythmia and heart failure. Radiotherapy is the treatment of choice to manage malignant effusions. In some instances, a pericardial window is required to treat tamponade. Chemotherapy has been used to prevent further cardiac involvement, but its use is limited by its cardiotoxicity. In rare instances, surgical debulking is indicated to alleviate obstructive cardiac masses.
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