Discrepancy of Hans' criteria for clonally related nodal and pericardiac fluid diffuse large B-cell lymphoma with MYD88 L265P mutation.

A 79-year-old Japanese woman presented with exertional dyspnea. She had cardiac tamponade and urgent pericardial drainage was performed. Pathological findings from the pericardial fluid revealed non-germinal center B-cell (non-GCB) pericardial large B-cell lymphoma (CD10^-, BCL6⁺, and MUM1⁺). Although a diagnosis of fluid overload-associated large B-cell lymphoma was considered, GCB nodal diffuse large B-cell lymphoma (CD10⁺, BCL6⁺, and MUM1⁺) was discovered through needle biopsy of the enlarged left axillary lymph node. Despite the two lymphomas exhibiting different expression levels of CD10, polymerase chain reaction assessing IgH gene rearrangement suggested a clonal relationship between them. Additionally, MYD88 L265P mutation was confirmed using Sanger sequencing in both samples, suggesting the MCD type. Our case highlights a discrepancy between the Hans' criteria and the gene expression profile-based cell of origin.