Fibrin-associated diffuse large B-cell lymphoma in an ovarian endometriotic cyst: a case report and review of the literature

Fibrin-associated diffuse large B-cell lymphoma (FA-DLBCL) is a rare, Epstein–Barr virus (EBV)-positive lymphoma typically occurring in immune-privileged, fibrin-rich environments. It shows an indolent course and is often incidental. While previously reported in thrombi, hematomas, and implants, no cases have been linked to endometriosis. We report the first documented case of FA-DLBCL arising in an ovarian endometriotic cyst. Case presentation A 59-year-old Asian woman with a history of endometriosis presented with progressive abdominal distension. Imaging revealed large cystic ovarian tumors, and bilateral adnexectomy was performed. Intraoperative findings included a 26-cm right ovarian mass comprising two tumors and a 13-cm left ovarian cyst. Histopathology of one right ovarian tumor revealed FA-DLBCL within a fibrin-rich, endometriotic cyst, confirmed by a cluster of differentiation (CD)20, CD30, and Epstein–Barr virus-encoded small RNA in situ hybridization (EBER-ISH) positivity. Serum EBV tests suggested prior infection. The patient remained recurrence-free for 2 years but subsequently developed a pelvic mass with markedly elevated CA 125 levels. Surgical resection revealed metastatic clear cell carcinoma without evidence of recurrent FA-DLBCL, and the patient was diagnosed with stage IIIA1(II) ovarian cancer. This is the first reported case of FA-DLBCL arising within an ovarian endometriotic cyst. FA-DLBCL typically develops in immune-privileged, fibrin-rich, and chronically inflamed environments. Endometriotic cysts share similar characteristics, including hemorrhage, chronic inflammation, and fibrin accumulation, suggesting a permissive microenvironment for EBV-driven lymphomagenesis. In this case, the tumor cells were sparsely distributed within fibrin and difficult to identify, underscoring the diagnostic challenge. Immunohistochemical screening, particularly with CD30 and EBER-ISH, was crucial for diagnosis. The FA-DLBCL component showed no recurrence after surgery; however, the patient later developed ovarian clear cell carcinoma, a known malignancy associated with endometriosis, and died despite treatment. This case underscores the importance of comprehensive histopathological evaluation and vigilant long-term follow-up in patients with endometriotic cysts, as multiple neoplastic processes, including lymphoma and carcinoma, may coexist and influence prognosis. It expands the spectrum of precursor lesions for FA-DLBCL to include endometriotic cysts.