The red pulp involvement in SMZL is more diffuse and consists of infiltration of cords as well as sinuses by neoplastic cells – both small lymphocytes as well as larger centroblasts or immunoblasts. Molecular Genetics: del 7q is found in about 40% of SMZL cases and it appears to be an adverse prognostic indicator. These patients show more frequent tumor progression. Immunoglobulin heavy-chain variable region (IgVH) shows somatic mutations in about half of cases. Alterations in p53 gene are rare in SMZL and associated with adverse outcome.