RT Journal Article SR Electronic T1 Cytological Features of Fibrin-associated Diffuse Large B-cell Lymphoma Arising in Retroperitoneal Pseudocyst: The First Case Report JF In Vivo JO In Vivo FD International Institute of Anticancer Research SP 1477 OP 1482 DO 10.21873/invivo.13594 VO 38 IS 3 A1 NA, KIYONG A1 KIM, SO-WOON A1 KIM, HYUN-SOO YR 2024 UL http://iv.iiarjournals.org/content/38/3/1477.abstract AB Background/Aim: Fibrin-associated diffuse large B-cell lymphoma (FA-DLBCL) is frequently associated with the Epstein-Barr virus (EBV) and manifests as non-mass-forming 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.