Fluid Overload-Associated Large B-Cell Lymphoma: A Case Report and Review of Literature.

Fluid overload-associated large B-cell lymphoma (FO-LBCL) is a new entity described in the fifth edition of the World Health Organization (WHO) Classification of Hematolymphoid Tumors (WHO-HAEM5). It refers to malignant lymphoma present with symptoms of serous effusions in body cavities (pleural, peritoneal, and/or pericardial) in the absence of an identifiable tumor mass. We present a case of an 82-year-old man with a history of atrial fibrillation and atrial flutter, status post-ablation, essential hypertension (HTN), hyperlipidemia (HLD), and diabetes mellitus (DM) type 2 who was referred to our hospital for shortness of breath due to recurrent pleural effusion. Right video-assisted thoracoscopy with right pleural biopsy was performed. Histopathological examination of the pleural biopsy revealed dense fibrous tissue, chronic inflammation, lymphoid aggregates, and granulation tissue, with no evidence of lymphoma. Cytology of the right pleural fluid revealed large lymphoid cells, which were positive for CD45, CD20, PAX-5, MUM-1, BCL2, BCL6, and MYC protein. They were negative for CD3, CD10, CD138, and HHV-8 by immunohistochemistry (IHC). Epstein-Barr virus (EBV) was negative by in situ hybridization (ISH). Due to the absence of any evidence of lymphoma elsewhere, a diagnosis of fluid overload-associated large B-cell lymphoma (FO-LBCL) was made. We provide a synopsis of the main clinicopathological features of FO-LBCL and the two main differential diagnoses, primary effusion lymphoma (PEL) and diffuse large B-cell lymphoma (DLBCL).