Primary cardiac lymphoma, diffuse large B-cell type (same case as previous image). The tumor was centered in the right ventricular myocardium and extended into the right atrium. The image shows high-grade lymphoma cells in the subendocardium. Given the rarity of primary cardiac lymphomas and a clinical presentation that mimics other cardiac conditions, the diagnosis is frequently delayed and often made post-mortem. The prognosis is poor, although some patients have achieved remission with newer chemotherapeutic approaches.