Three Years of Idiopathic Chylous Ascites: Splenic Marginal Zone Lymphoma Behind the Mask

Chylous ascites is rare in adults and is most commonly caused by lymphatic obstruction due to non-Hodgkin B-cell lymphoma. Splenic marginal zone lymphoma (SMZL) is an uncommon etiology. We report the case of an 89-year-old man with a three-year history of refractory chylous ascites initially considered of unknown origin. Clinical examination revealed significant ascites and splenomegaly. PET imaging demonstrated hypermetabolic lymphadenopathy, and bone marrow biopsy revealed infiltration by a CD5-/CD10- B-cell lymphoma consistent with SMZL. Analysis of ascitic fluid showed a predominance of T lymphocytes without a detectable B-cell clone. This case illustrates that SMZL, although rare, should be included in the differential diagnosis of persistent chylous ascites. A comprehensive diagnostic approach combining imaging, bone marrow biopsy, and flow cytometry is essential to establish a timely diagnosis and guide appropriate management, especially in elderly patients.