Diffuse infiltrative primary cardiac lymphoma with delayed extracardiac involvement.

Primary cardiac lymphoma (PCL) is an extremely rare and fatal neoplasm of the heart. Traditionally, it is defined as lymphoma involving the heart or pericardium. PCL has a poor prognosis because of the diagnostic difficulty and its location. We present the case of a 48-year-old man who presented with pericardial effusion and diffuse cardiac wall thickening. We first suspected infiltrative heart disease. However, even after performing a biopsy, we could not establish an accurate diagnosis. After 20 months, primary cardiac diffuse large B cell lymphoma (DLBCL) was diagnosed by cervical lymph node biopsy. In this case, after chemotherapy, the DLBCL lesions, including cardiac wall thickening, improved. The treatment outcome suggests that the diagnosis was diffuse infiltrative PCL with delayed extracardiac involvement.