Lymphomas of the marginal spleen zone are an entity recently considered as separate by the International Lymphoma Study Group. There are B-cell non Hodgkin's lymphomas (NHL) of low grade malignancy with a characteristic phenotype that allows to differentiate from mantle lymphomas and other B-cell lymphoproliferative syndromes. The case of a 69-year-old female patient admitted for abdominal pain due to large splenomegaly is reported. Pancytopenia and the presence of atypical large-sized lymphocytes with extensive cytoplasm and a rounded nucleus with indentations, reticulated appearing chromatin and one or several nucleoli were of note in the hemogram. Microscopic examination of the bone marrow demonstrated moderate-degree lymphocytary infiltration with grade I reticulin fibrosis. Laparotomy with splenectomy was performed. White pulp invasion with multifocal infiltration of the red pulp by lymphocytes of the same characteristics as those observed in the peripheral blood and bone marrow were observed on microscopic bone marrow examination. Immunophenotypic study of these lymphocytes was positive for CD19, CD20 and CD22 while being negative for CD5, CD10, CD23, CD25, CD11c and FMC7, the phenotype belonging to the lymphocytes of marginal spleen zone. Following splenectomy the patient recovered hemoperipheral counts and did not undergo additional treatment. The patient died due to septic shock of respiratory origin 4 months later. The clinical, morphologic and immunophenotypic features of marginal spleen zone lymphomas are reported with emphasis on the differences with other B-cell non Hodgkin's lymphomas of low malignancy.