Fibrin-associated large B-cell lymphoma: part of the spectrum of cardiac lymphomas.

Cardiac lymphomas are rare, and the spectrum of pathologic features is not well defined. We encountered an unusual case of cardiac lymphoma residing within a presumed thrombus. To place such cases in context, we reviewed all cardiac lymphomas presenting to a large US cardiovascular medicine referral center during a 30-year period. A total of 14 cardiac lymphomas were identified, and these included 6 primary cardiac lymphomas (PCLs) and 8 lymphomas secondarily involving cardiac structures. Upon review, 3 of the PCLs were confirmed to be diffuse large B-cell lymphoma, not otherwise specified, involving the myocardium. The other 3 cases of PCL lacked myocardial invasion and showed lymphoma cells embedded in fibrin thrombus. Acute inflammation was not evident. These lymphomas presented in immunocompetent male individuals and involved either a prolapsed myxomatous mitral valve, a pseudomyxoma from the left atrium, or a thrombus arising in a synthetic aortic root graft. All 3 consisted of large atypical lymphocytes expressing a nongerminal center B-cell immunophenotype. Two cases were positive for Epstein-Barr virus (latency type III), but none demonstrated human herpes virus-8 latent nuclear antigen. No systemic disease was found at presentation or during follow-up. In our experience, fibrin-associated large B-cell lymphoma arising in the heart represents a substantial proportion of PCL. These lymphomas appear to represent an underrecognized variant of diffuse large B-cell lymphoma with favorable outcome. Further study is needed to understand their natural history.