Marginal zone lymphoma presenting with chylous ascites: A rare clinical manifestation and successful treatment with orelabrutinib–rituximab

Marginal zone lymphoma is the second most common subtype of indolent non-Hodgkin lymphoma. Its clinical manifestations are heterogeneous and largely determined by the involved site. Chylous ascites, as the initial presentation of marginal zone lymphoma, is extremely rare. We report a 79-year-old man who presented with rapidly progressive abdominal distension due to high-volume chylous ascites. Flow cytometry of the ascitic fluid revealed a monoclonal lambda-restricted B-cell population consistent with low-grade B-cell lymphoma. Bone marrow biopsy confirmed splenic marginal zone lymphoma. Initial rituximab monotherapy was ineffective; however, combination therapy with orelabrutinib and rituximab led to complete resolution of ascites after two cycles and marked disease control. At 6-month follow-up, the patient remained in remission. Clinicians should consider lymphoma in the differential diagnosis of unexplained chylous ascites. Prompt etiologic treatment can result in favorable outcomes even in elderly patients with advanced disease.