De novo CD5-positive primary cardiac diffuse large B-cell lymphoma diagnosed by pleural fluid cytology.

Primary cardiac lymphomas are exceedingly rare. The presence and extent of the intracardiac mass is determined by echocardiography, computed tomography (CT), or magnetic resonance imaging (MRI); however, the diagnosis is established by endomyocardial biopsy or by pericardial or pleural effusion cytology. We describe the pleural effusion cytologic features of a primary cardiac lymphoma in a 55-year-old woman who presented with progressive shortness of breath, fatigue, mild dizziness, dull chest ache, and lower extremity edema. Transthoracic echocardiography, CT, and MRI showed a large mass centered in the right atrium and extending into the right ventricle, associated with pericardial effusion and bilateral pleural effusions. Cytologic examination of the pleural fluid showed very large pleomorphic malignant cell, some of which were binucleated and multinucleated and had anaplastic features. Flow cytometry showed a kappa monotypic population of large cells coexpressing CD5, CD19, and CD20; and immunoperoxidase stains performed on the cell block sections showed that the large neoplastic cells were positive for CD20, PAX5, CD5, and MUM1 and showed a very high proliferation rate (over 90%) by Ki67 staining. The cytologic, flow cytometry, and immunohistochemistry findings established the diagnosis of de novo CD5-positive primary cardiac diffuse large B-cell lymphoma (DLBCL), anaplastic variant, which was confirmed by the subsequent endomyocardial biopsy. This is, to the best of our knowledge, the first report of de novo CD5-positive primary cardiac diffuse large B-cell lymphoma, and the first report of the anaplastic variant of DLBCL diagnosed by effusion cytology.