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Introduction

Follicular lymphoma was previously known as follicle centre cell lymphoma, poorly differentiated lymphocytic lymphoma and centroblastic/centrocytic lymphoma. It is a disease of adult life, occurring in young, middle aged and elderly adults. It is rare in children and adolescents. Paediatric-type follicular lymphoma and primary cutaneous follicular lymphoma are considered separate disease entities in the World Health Organization (WHO) classification [1, 2] and are discussed at the end of this chapter. In contrast to most other lymphoproliferative disorders, there is a somewhat higher incidence in women. It is a low-grade malignancy. Although many patients (around 80%) present with wide-spread disease, with the advent of novel therapies median survival is of the order of 10–15 years. Follicular lymphoma arises from a germinal centre B cell showing ongoing somatic hypermutation of IGHV. Distinct variants of follicular lymphoma, testicular and duodenal follicular lymphomas, have characteristic clinical and biological features.

Clinical features

Patients usually present with lymphadenopathy. Sometimes the spleen is also enlarged and Waldeyer’s ring may be involved. Occasionally, the diagnosis is incidental in an asymptomatic patient. Even widespread disease is often relatively asymptomatic but some patients with advanced disease have B symptoms (fever, weight loss and night sweats). Patients with advanced disease may have pleural or pericardial effusions or ascites. Spontaneous remissions, with subsequent relapse, are sometimes observed. Rarely, a spontaneous remission occurs and on prolonged follow-up there is no relapse. Transformation to diffuse high-grade B-cell lymphoma can occur. Testicular follicular lymphoma is more frequent in children and has a good prognosis. Primary duodenal follicular lymphoma affects the small intestine, frequently the duodenum and needs to be distinguished from secondary involvement of the intestine by nodal follicular lymphoma [3].

Haematological and pathological features

The peripheral blood may be normal or there may be a greater or lesser number of circulating lymphoma cells [4]. Cytological characteristics differ between patients (Figures 5.1, 5.2, 5.3). Some patients, particularly those with large numbers of circulating lymphoma cells, have very small cells, smaller than those of chronic lymphocytic leukaemia, with scanty cytoplasm; the nuclei show evenly condensed (rather than clumped) chromatin and deep, very narrow clefts. In other patients, the cells are larger and more pleomorphic with less condensed cytoplasm and often a visible nucleolus; some cells have nuclear clefts, which are characteristically deep and narrow with parallel edges. Cells are less fragile than those of chronic lymphocytic leukaemia so that smear cells are less often a feature. Although in the past blood involvement by follicular lymphoma had been considered an adverse prognostic factor, at present with the use of rituximab maintenance therapy, this is no longer the case [5]. Anaemia and thrombocytopenia are uncommon at presentation, but may be seen in patients with advanced disease.

Figure 5.1

Peripheral blood film in follicular lymphoma showing mature lymphocytes with ...

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