[Clinicopathological features of fibrin-associated diffuse large B-cell lymphoma: a report of six cases]

Objective: To investigate the clinical, pathological and immunophenotypic features, molecular biology and prognosis of fibrin-associated large B-cell lymphoma (LBCL-FA) in various sites. Methods: Six cases of LBCL-FA diagnosed from April 2016 to November 2021 at the Beijing Friendship Hospital, Capital Medical University, Beijing, China and the First Affiliated Hospital, Wenzhou Medical University, Wenzhou, China were collected. The cases were divided into atrial myxoma and cyst-related groups. Clinical characteristics, pathological morphology, immunophenotype, Epstein Barr virus infection status, B-cell gene rearrangement and fluorescence in situ hybridization of MYC, bcl-2, bcl-6 were summarized. Results: The patients' mean age was 60 years. All of them were male. Three cases occurred in atrial myxoma background, while the others were in cyst-related background, including adrenal gland, abdominal cavity and subdura. All cases showed tumor cells located in pink fibrin clot. However, three cyst-related cases showed the cyst wall with obviously fibrosis and inflammatory cells. All cases tested were non germinal center B cell origin, positive for PD-L1, EBER and EBNA2, and were negative for MYC, bcl-2 and bcl-6 rearrangements, except one case with MYC, bcl-2 and bcl-6 amplification. All of the 5 cases showed monoclonal rearrangement of the Ig gene using PCR based analysis. The patients had detailed follow-ups of 9-120 months, were treated surgically without radiotherapy or chemotherapy, and had long-term disease-free survivals. Conclusions: LBCL-FA is a group of rare diseases occurring in various sites, with predilection in the context of atrial myxoma and cyst-related lesions. Cyst-related lesions with obvious chronic inflammatory background show more scarcity of lymphoid cells and obvious degeneration, which are easy to be missed or misdiagnosed. LBCL-FA overall has a good prognosis with the potential for cure by surgery alone and postoperative chemotherapy may not be necessary.