ABSTRACT
Primary cardiac lymphoma (PCL) is a rare and fatal disorder. It may often mimic other common cardiac tumors like cardiac myxoma because of similarities in the clinical presentation. We report a case of PCL of diffuse large B-cell type, in a 38-year-old, immunocompetent male who presented with superior vena cava syndrome that was excised as a myxoma. Histology revealed a large cell population diffusely and strongly expressing CD45, CD20, MUM1/IRF4 and FOXP1 hinting at an activated B-cell (ABC)-like phenotype. After four cycles of Rituximab with CHOP (cyclophosphamide, hydroxydaunorubicin, Oncovin, and prednisolone) the tumor regressed completely but the patient had a relapse and subsequently succumbed to the disease confirming the aggressive nature. The aggressive behavior of PCL may be possibly linked to its ABC-like origin.