Large B-cell lymphoma associated with fluid overload: two new case reports with molecular insights

The 5th edition of the World Health Organization (WHO) and the International Consensus Classification (ICC 2022) recently recognized a subtype of diffuse large B cell lymphoma (DLBCL), respectively called fluid overload-associated large B-cell lymphoma (FO-LBCL) and human herpes virus 8 (HHV8)/Epstein-Barr (EBV)-negative primary effusion-based lymphoma. However, few reports have provided a molecular profile for this entity. We present two cases, both females, who presented to our hospital with, respectively, massive pleural and pericardial effusion, but with no other significant pathological findings, and for both of whom FO-LBCL was the final diagnosis. Both cases exhibited activated and germinal center phenotypes but had distinct mutational profiles. In this report, we consider the diagnosis, focusing on the main clinicopathological features that differentiate it from primary effusion lymphoma (PEL) and other DLBCL subtypes. We report the results of a next generation sequencing study carried out to provide new evidence about the molecular pathogenic mechanisms of this rare, recently described entity.