Mantle cell lymphoma is a B-cell neoplasm that affects adults . There is a marked male predominance. Aetiology is unknown. The grade of malignancy is intermediate between that of follicular lymphoma and that of diffuse large B-cell lymphoma, hence the previous designations 'lymphoma of intermediate differentiation' and 'intermediate lymphoma'. Other earlier designations include diffuse centrocytic lymphoma, diffuse small cleaved cell lymphoma, diffuse small and large cleaved cell lymphoma, diffuse large cleaved cell lymphoma and mantle zone lymphoma. Some of these designations are confusing: there is, for example, no relationship between this type of lymphoma cell and the centrocyte. The lymphoma cell is believed to be analogous to a mantle zone cell rather than a 'centrocyte' (follicular centre cell). Mantle cell lymphoma most often arises in a pre-germinal-centre B-cell that does not show somatic hypermutation of IGVH; however about one-third of cases do show somatic mutation.
Many patients present with advanced disease (stage III or IV) . Lymphadenopathy, hepatomegaly and splenomegaly are common and involvement of bone marrow and peripheral blood is often present. Gastrointestinal involvement, as multiple lymphomatous polyposis, is detected in about one-third of patients but, if biopsies are carried out routinely, some degree of infiltration is found to be much more common, being detected in most patients. Involvement of Waldeyer's ring, including the tonsil, is present in a significant minority of patients.
Haematological and pathological features
Circulating lymphoma cells are often present, being reported in 20-40% of cases . They tend to be medium sized with some degree of pleomorphism with regard to cell size and the shape of the cell and the nucleus (Figures 6.1, 6.2, 6.3). Some cleft and irregular nuclei are often present and there may be small nucleoli; the chromatin pattern may be condensed or speckled. Cytoplasm is scanty and weakly basophilic. In a minority of patients the disease is characterized as small cell type or as pleomorphic or blastoid variant. In the small cell type there is a round or slightly indented nucleus with dense chromatin; confusion with chronic lymphocytic leukaemia (CLL) can occur. In the pleomorphic variant, cells are medium sized and large with more cytoplasm, in some cases resembling prolymphocytes and in others being more pleomorphic. Cells of the blastoid variant are more monomorphic with a dispersed chromatin pattern (Figure 6.4) so that confusion with acute lymphoblastic leukaemia can occur.
Peripheral blood film in mantle cell lymphoma showing pleomorphic cells; some have irregular nuclei and many are nucleolated. Romanowsky, x 60 objective.
Peripheral blood film in mantle cell lymphoma showing pleomorphic cells with variable nuclear shape and variable chromatin condensation.