Mantle-cell lymphoma.

Histological subtyping of non-Hodgkin's lymphomas is of prognostic significance. Current classification systems subdivide them into low-, intermediate-, and high-grade malignancies. These subgroups are largely supported by clinical findings, but immunophenotyping and genotyping have shown that several of these histologically defined subcategories are heterogeneous. This is exemplified by the 'diffuse small cleaved-cell lymphoma' which comprises B-cell and T-cell lymphomas. Moreover, within the B-cell lymphomas, several entities have been included, which recapitulate the different compartments present in the reactive B follicle, e.g., the follicle centre, the mantle, and the marginal zone. Mantle-cell lymphomas have been identified in the United States as mantle-zone lymphomas and as intermediate differentiated lymphomas and in Europe as centrocytic lymphomas. Morphology, immunophenotyping, and cytogenetics of these three lymphomas support their similarity and underline their distinction from follicle centre-cell lymphomas as well as from small lymphocytic lymphomas. All three are composed of a mixture of small round and small cleaved cells, expressing several B-cell markers, surface immunoglobulins, and CD5, but lacking CD10 expression. They often carry the translocation t(11;14) with rearrangement of bcl-1/PRAD1 gene. The behaviour and responsiveness to therapy of mantle-cell lymphomas has not been fully documented yet. In order to obtain these data, precise subtyping of non-Hodgkin's lymphomas--not only based on morphology, but supported by immunophenotyping and cytogenetic analysis--is now mandatory.