Splenic marginal zone lymphoma uncovered after a 10-year follow up as anemia of unknown cause

A 75-year-old man was referred to our hospital for evaluation of persistent anemia. Despite repeated diagnostic tests, including bone marrow aspiration, the cause of his anemia remained unknown. On each occasion, computed tomography had revealed neither swollen lymph nodes nor splenomegaly. After a 10-year follow-up period, he was admitted with general fatigue and had developed splenomegaly as well as the anemia. Bone marrow biopsy revealed increased abnormal lymphocytes with short villi that were positive for CD11c, CD19, CD20, and kappa chain, but not for CD5, CD10, CD23, or cyclin D1, according to flow cytometry. The bone marrow biopsy sample showed nodular proliferation of small to medium-sized abnormal lymphocytes. Based on these findings, the patient was diagnosed as having splenic marginal zone lymphoma, a rare indolent B-cell neoplasm. Although his splenomegaly diminished after eight cycles of weekly rituximab monotherapy, the anemia did not improve, and abnormal lymphocytes remained detectable in his bone marrow. The patient was then treated with bendamustine monotherapy for six cycles, after which the anemia resolved, and he has since been in good condition. Although rare, it is important to consider splenic marginal zone lymphoma during the differential diagnosis of patients with a long history of anemia of unknown cause.