Diffuse Large B-Cell Lymphoma Presenting in a Background of Rosai-Dorfman Disease.

Rosai-Dorfman disease (RDD) can present with lymphadenopathy. However, it is important to note that RDD can also coexist with hematologic malignancies, including non-Hodgkin lymphomas. We present a case of an older male patient with generalized lymphadenopathy who was first diagnosed with RDD. High-dose steroid therapy was rendered without a satisfactory response. Thus, the tissue specimens were re-examined, and the patient was found to have diffuse large B-cell lymphoma (DLBCL) in the background of RDD. The laboratory tests are notable for a slightly elevated serum lactate dehydrogenase (LDH) level. A positron emission tomography-computed tomography scan revealed generalized hypermetabolic lymphadenopathy above and below the diaphragm. A bone marrow biopsy showed normocellular marrow without evidence of DLBCL. The international prognostic index score was 3 (age > 60 years, elevated serum LDH level, and Stage III disease), indicating a high-intermediate risk disease. The patient was treated with six cycles of golcadomide in combination with R-Pola-CHP (rituximab, polatuzumab vedotin, cyclophosphamide, doxorubicin, and prednisone) for the underlying DLBCL, with resolution of both DLBCL and RDD. The disease remained in remission at the follow-up visit 9 months after completing the therapy. This case highlights the importance of recognizing underlying DLBCL in patients with RDD for optimal patient outcomes. Trial Registration: ClinicalTrials.gov identifier: NCT04884035.