**1. Introduction**

B-cell lymphomas are malignant neoplasms that arise from different stages of differentiation of B-cells and constitute a broad spectrum, extending from small- to large-cell types, and from low to high grades of clinical behavior. It constitutes the major type of non-Hodgkin's lymphoma (NHL) [1–3].

The recognition of lymphoma evolved from Thomas Hodgkin's 1832 paper entitled "On Some Morbid Appearances of the Absorbent Glands and Spleen" [4], followed by various nomenclatures and classifications that classified lymphomas into Hodgkins and non-Hodgkin's lymphomas [5–11]. In 1974, Lennert et al. [12] and Lukes and Collins [13] classified NHL on the basis of the cell of origin as B cell lymphomas and T cell lymphomas which was later confirmed at the molecular level with the identification of specific Ig gene and T-cell receptor (TCR) gene rearrangements [14–17]. In 1982, a Working Formulation (WF) classified NHL according to histologic grade as low, intermediate, and high [18]. In 1994, a Revised European American Lymphoma (REAL) Classification was proposed which diagnosed lymphomas by identifying clinical features, morphology, immunophenotype, and genetic data [19]. The World Health Organization (WHO) then adopted the diagnostic principles of the REAL Classification, and is used as the schema for the diagnosis of all hematopoietic neoplasms [20, 21].

The 2001 and 2008 World Health Organization classification of hematopoietic and lymphoid tumors established guidelines for the diagnosis of malignant lymphomas; however, subsequently, there have been major advances with significant clinical and biologic implications which necessitated further revisions [22, 23]. Hence further revision was done in 2016 which reflects a consensus among hematopathologists, geneticists, and clinicians regarding both updates to current entities as well as the addition of a limited number of new provisional entities leading to more targeted therapeutic strategies. The current WHO classification uses morphologic, immunophenotypic, genotypic, and clinical features to classify the lymphoid neoplasms into five broad categories as precursor B-cell neoplasms, peripheral B-cell neoplasms, precursor T-cell neoplasms, peripheral T-cell neoplasms and Hodgkin lymphoma. Hodgkin lymphoma though originates from B-cell has distinctive pathologic features and is treated as a separate entity**.** This chapter discusses about the etiology and pathogenesis, clinical features, recent WHO classification of B-cell lymphomas (2017), the highlights of modifications brought in, the morphology, immunophenotype, staging, treatment and prognosis of various B-cell lymphomas [24–26].
