In a study of 31 patients with both cancer and pericardial effusions, malignant pericardial effusion accounted for 58% of the effusions, 32% were caused by benign idiopathic pericarditis, and radiation pericarditis caused 10% of cases.[11,12]
Malignant involvement of the pericardium is the most common reason for development of pericardial effusions, which result from blockage of venous and lymphatic circulation of pericardial fluid. Such blockage may be caused by primary malignancy of the pericardium, as with pericardial mesothelioma, or by tumors arising in the myocardium, including angiosarcoma, rhabdomyosarcoma, and malignant fibrous histiocytosis. Malignancies can also involve the pericardium through direct extension from carcinomas of the lung or esophagus, thymoma, or lymphoma. Lymphatic or hematogenous metastasis to the pericardium occurs most commonly with carcinomas of the breast and lung, leukemia, lymphoma, and melanoma. Primary tumors of the pleura or pericardium have recently been termed primary intrathoracic malignant effusions.
Nonmalignant causes of pericardial effusion include pericarditis, myocardial infarction, uremia, hypothyroidism, systemic lupus erythematosus, trauma, postsurgical pericardotomy syndrome, and intrapericardial hematomas.[14,15,16] AIDS may also cause pericardial effusion with pericarditis. Radiation therapy or chemotherapy drugs can cause pericarditis without metastatic involvement of the pericardium. Radiation pericarditis is usually associated with radiation doses to the cardiac window exceeding 3,000 cGy  and occurs most frequently in patients who have received mediastinal radiation for Hodgkin disease or breast cancer. Doxorubicin and cyclophosphamide have been associated with the development of acute pericarditis with effusions.[11,12] Other drugs that may cause acute pericarditis include procainamide, hydralazine, isoniazid, methysergide, phenytoin, and anticoagulants.
Pericardial tamponade results from progressive fluid accumulation in the pericardial sac, causing elevated intrapericardial pressure, diminished stroke volume, decreased cardiac output, progressive decrease in cardiac diastolic filling, and hemodynamic compromise resulting in death if not treated. Hemodynamic compromise occurs when the normal amount of pericardial fluid (approximately 15–50 cc) increases to 200 cc to 1,800 cc.[15,18] When fluid accumulates rapidly, as little as 250 cc of fluid can result in tamponade.[11,19]