We present the case of a 65 years old male, admitted in the Hematology Department of the Universitary Emergency Hospital Bucharest, complaining of physical asthenia and weight loss; periodical medical examination has revealed splenomegaly and leucocytosis with lymphocytosis, persistent for the past 3 years. The clinical and paraclinical exam demonstrated splenomegaly (21 cm in diameter on computer tomography scan), hepatomegaly and generalized lymphadenopathies. The laboratory tests confirmed leucocytosis with lymphocytosis--a clonal population of B lymphocytes CD20+ CD19+ CD23+/- CD79b+(low), CD43+ FMC7+ CD5+ CD38+ ZAP70+ cyclin D1-. Lymph node and bone marrow biopsy together with flowcytometry established the diagnosis of Malignant non-Hodgkin Lymphoma--Atypical Splenic Marginal Zone B-cell lymphoma (aberrant expression of CD5) stage IVB, with leukemic picture, complicated with autoimmune hemolytic anemia with highly positive Coombs' tests. We performed therapeutic splenectomy, which was difficult because of the dimensions of the organ. The short term evolution was complicated by acute complete thrombosis of the splenic vein, but the long term evolution (1 year follow-up) was favorable--remission of anemia, significant improvement of performance status, decrease of leucocytosis and reduction of the tumoral mass.