Primary Malignant Pericardial Epithelioid Mesothelioma Presenting as Cardiac Tamponade: A Case Report With Multimodality Imaging and Radiologic-Pathologic Correlation.

Primary malignant pericardial mesothelioma is an exceptionally rare and aggressive malignancy that frequently presents with nonspecific cardiopulmonary symptoms, recurrent pericardial effusion, constrictive physiology, or cardiac tamponade. Early diagnosis is challenging because an infiltrative pericardial tumor may remain occult on initial imaging studies performed for acute cardiopulmonary evaluation. A 67-year-old woman presented with chest discomfort and shortness of breath. CT pulmonary angiography and thoracic aortic computed tomography angiography (CTA) were performed to evaluate for pulmonary embolism and acute aortic pathology. The examinations were negative for pulmonary embolism and acute aortic abnormality; however, they revealed a large mildly hyperattenuating circumferential pericardial effusion measuring approximately 35 HU, concerning for complex mixed hemorrhagic and serous fluid with tamponade physiology. No discrete enhancing pericardial mass was confidently identified on the initial CTA examination. Transthoracic echocardiography confirmed a large pericardial effusion with tamponade physiology. Pericardiocentesis removed approximately 600 cc of fluid, with cytologic analysis nondiagnostic for malignant cells. The patient returned approximately 2 weeks later with progressive dyspnea. Cardiac MRI demonstrated an extensive heterogeneously enhancing infiltrative anterior pericardial mass extending toward the great vessels and left atrial region. FDG PET/CT showed an intensely FDG-avid infiltrative pericardial mass without distant metastatic disease or FDG-avid lymphadenopathy. Thoracoscopy and pericardial biopsy confirmed epithelioid mesothelioma. Immunohistochemistry revealed positivity for CK7, calretinin, CK5/6, and WT1 and negativity for claudin-4 and TTF-1. The patient was treated with carboplatin and pemetrexed, with planned radiation therapy. This case highlights that primary malignant pericardial mesothelioma may initially present as complex hemorrhagic pericardial effusion with tamponade physiology, with infiltrative tumor occult on nondedicated acute CTA examinations. Persistent or recurrent symptoms following drainage should prompt further evaluation with cardiac MRI and PET/CT for tissue characterization, staging, and biopsy planning.