Background/Aim: Fibrin-associated diffuse large B-cell lymphoma (FA-DLBCL) is frequently associated with the Epstein-Barr virus (EBV) and manifests as non-massforming microscopic lesions within fibrin-rich lesions. Herein, we describe the cytological features of FA-DLBCL. Case Report: A 72-year-old man presented with a large retroperitoneal cystic mass that was treated by cyst aspiration and laparoscopic excision. Individually dispersed large, atypical cells in a necrotic background contained scant cytoplasm and hyperchromatic nuclei with irregular nuclear contours, frequent karyorrhectic debris, and mitotic figures. A fibrinous exudate with necrotic material attached to the inner surface of the cystic mass contained large, atypical cells that were individually scattered or arranged in small clusters. These were positive for cluster of differentiation 20 and Epstein-Barr virus-encoded RNA in situ hybridization. Conclusion: We cytologically characterized FA-DLBCL as large, atypical cells that were individually scattered or arranged in small clusters in a necrotic background. To the best of our knowledge, we revealed the cytological features of FA-DLBCL.Fibrin-associated diffuse large B-cell lymphoma (FA-DLBCL) is a neoplasm of large B-cells that is incidentally found at sites of chronic fibrin deposition (1). It is an unusual form of DLBCL associated with chronic inflammation (DLBCL-CI) (2). Like DLBCL-CI, FA-DLBCL involves the proliferation of Epstein-Barr virus (EBV) infected large B-cells located in restricted anatomical spaces that afford protection against the immune system (3). However, FA-DLBCL should perhaps be regarded as a nonmalignant or pre-malignant lymphoproliferative disorder rather than malignant DLBCL-CI (4) because it is indolent with the potential for a surgical cure (5). Fibrin-associated DLBCL manifests as non-mass-forming, microscopic lesions within fibrin-rich lesions (2,6). Owing to its rarity and unique clinical presentation, FA-DLBCL poses significant diagnostic challenges for practicing pathologists. To the best of our knowledge, the cytological features of FA-DLBCL have not been published. This report describes the cytological features of FA-DLBCL in liquid-based preparation (LBP) and conventional smear (CS) specimens for the first time. Our findings improve the understanding of this rare entity and offer insights for pathologists facing decisive cytological diagnoses.