EBV+ diffuse large B-cell lymphoma arising within atrial myxoma. An example of a distinct primary cardiac EBV+ DLBCL of immunocompetent patients.

Cardiac myxoma and diffuse large B-cell lymphoma are uncommon tumors, yet four composite tumors have been reported since 2009. We are reporting on the fifth case providing detailed immunohistochemical and FISH analyses. The lymphoma was present as superficially located nests of large cells with patchy necrosis in the background of a typical atrial myxoma. It displayed features of DLBCL with non-germinal center phenotype, expressed EBER, LMP1, EBNA2 and shared the following features with the previously reported cases: B-cell lineage, high-grade cytology, high proliferation rate, EBV infection in latency type 3 with one tested case and an excellent outcome. The lymphomas arising within myxoma may follow a pathogenic pathway driven by EBV, whose transformation potential is unleashed in the cytokine-rich milieu of a myxoma, presumably accentuating age-related decline of adaptive immunity known as immune senescence. DLBCL arising within atrial myxoma grouped together with EBV+ DLBCL associated with valve prosthesis and with an atrial thrombus differs in the immunocompetent patients from primary cardiac DLBCL, not otherwise specified, in clinical presentation, pathological features and a course of the disease. Distinction between these groups may have important therapeutic consequences.