Fibrin-associated large B-cell lymphoma arising in benign gynecologic tumors: insights into disease spectrum expansion and pathophysiology.

Fibrin-associated large B cell lymphoma is a rare Epstein-Barr virus-positive lymphoma arising in restricted anatomical spaces, predominantly in immunocompetent individuals; its clinical behavior and pathophysiology remain unclear. We report two cases of fibrin-associated large B cell lymphoma that were incidentally detected in bulky uterine leiomyomas and ovarian fibromas. The first patient presented with limited-stage disease and showed an indolent clinical course, managed with surgery alone; the second presented with advanced-stage disease with malignant pleural effusion, requiring chemotherapy. Lymphoma cells in the pleural effusion shared an immunohistochemical staining profile with the primary site, and genomic analysis confirmed B cell clonality. Both patients shared an unusual Epstein-Barr virus latency pattern, possibly reflecting a locally immunosuppressed microenvironment. These cases broaden the recognized spectrum of fibrin-associated large B cell lymphoma and highlight that, although typically localized, the disease may present with concomitant involvement of multiple sites at diagnosis.