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Introduction

Mantle cell lymphoma (MCL) is a B-cell neoplasm that affects adults [1]. 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). MCL most often arises in a pre-germinal-centre B cell that does not show somatic hypermutation of IGVH; however, about one-third of the cases do show somatic mutation and so are of post-germinal centre origin.

Clinical features

Many patients present with advanced disease (stage III or IV) [2]. Lymphadenopathy, hepatomegaly and splenomegaly are common and involvement of bone marrow and peripheral blood is often present. Some cases manifest with leukaemia and often splenomegaly but without lymphadenopathy. These non-nodal leukaemic forms are categorized as a distinct variant according to the 2016 WHO classification [1]. Gastrointestinal involvement, as multiple lymphomatous polyposis, is detected in about one-third of patients but, if biopsies are carried out routinely, some degree of bowel 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. Another variant is in situ mantle cell neoplasia (previously in situ mantle cell lymphoma), which is defined by the presence of cyclin D1-positive cells and CCND1 rearrangements confined to the mantle zone of the follicles within a hyperplastic lymph node; several nodes or extranodal sites may be affected. There are controversies regarding to the risk of progression to MCL.

Haematological and pathological features

Circulating lymphoma cells are often present, being reported in 20%–40% of cases [3]. 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, marginal-zone-like 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 marginal zone-like MCL, the cells have abundant pale cytoplasm resembling monocytoid cells. In the pleomorphic variant, cells are medium sized and large ...

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