Splenic marginal zone lymphoma (SMZL) has been recognized as a distinctive type of small B cell lymphoma, and defined on the basis of its morphological, phenotypic, clinical and molecular characteristics. In spite of this, the borders of the entity, the homogeneity of the cases and the presumably cell origin of SMZL remain controversial issues. The frequency of mutation in the 5′ non-coding region of the bcl-6 gene has been used as a marker of germinal center derivation, which may be used to establish the molecular heterogeneity of different non-Hodgkin lymphoma (