Primary Cardiac Diffuse Large B-cell Lymphoma Promptly and Safely Diagnosed with Pericardial Effusion Cytology: A Case Report.

: Primary cardiac lymphoma is a rare condition with a poor prognosis, and patients are at risk for sudden cardiac death. A prompt diagnosis and early treatment are therefore essential. A 68-year-old woman was admitted for shortness of breath and peripheral edema. Echocardiograms showed massive pericardial effusion and a mass on the free wall of the right atrium and ventricle. Subsequent pericardial effusion cytology revealed diffuse large B-cell lymphoma. We started chemotherapy with rituximab and achieved a good clinical course. This case is made unique by the use of pericardial effusion cytology, which allowed us to diagnose primary cardiac lymphoma promptly and safely.