Abstract
Fibrin-associated large B-cell lymphoma (FA-LBCL) is an extremely rare subtype of LBCL that consists of microscopic aggregates of atypical large B cells in the background of fibrin. Here, we report the first case of FA-LBCL in Korea. A 57-year-old male presented with a large amount of thrombus in the thoracic aorta during follow-up for graft replacement of the thoracoabdominal aorta 8 years prior. The removed thrombus, measuring 4.3 × 3.1 cm, histologically exhibited eosinophilic fibrinous material with several small clusters of atypical lymphoid cells at the periphery. The atypical cells were positive for CD20 by immunohistochemistry and for Epstein-Barr virus by in situ hybridization. The Ki-67 proliferation rate was 85%. The patient was still alive with no recurrence at the 7-year follow-up after thrombectomy. Although the diagnosis can be very difficult and challenging due to its paucicellular features, pathologists should be aware of FALBCL, which has likely been underestimated in routine evaluations of thrombi.