Diffuse Large B-Cell Lymphoma Masquerading as Recurrent Pleural Effusion and Melena: A Case Report and Literature Review.

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma, accounting for roughly one-third of adult cases worldwide. Typically, patients have a rapidly enlarging mass at presentation, which could be a lymph node or mass lesion anywhere in the body. However, extranodal manifestations and B symptoms can also be observed, and often two-thirds of the patients already present as advanced-stage DLBCL. Early diagnosis of the disease is essential, as early initiation of treatment for advanced stages gives a five-year survival rate of 50-60%. Therefore, it is imperative to recognize unusual presentations of DLBCL and include it in our differential in patients with uncommon extranodal manifestations. We report the case of a 76-year-old man who presented with recurrent pleural effusion and gastrointestinal bleeding and was ultimately diagnosed with multisite extranodal DLBCL involving the stomach, liver, and pleura. The initial presentation raised concerns for primary thoracic or gastrointestinal malignancy, contributing to diagnostic uncertainty. Early recognition of atypical presentations is essential to avoid delays in diagnosis and facilitate timely treatment.