Follicular Lymphoma: Definition, Epidemiology, Pathobiology – Lymphomagenesis, Morphology, Variants, Immunophenotype, Prognostic Factors, Transformation

Follicular lymphoma is the most common, indolent lymphoma in the western world; this chapter discusses the pathobiology that will touch upon the evolutionary history and the role of germinal centers that provide a landscape for B cells to acquire oncogenic mutations leading to malignant transformation. The molecular alterations leading to disease progression, divergent evolutionary pathway, and the role of microenvironment are discussed. The morphological variants and clinical-histologic variants, immunophenotype, prognostic factors, and differential diagnosis are discussed. In summary, the chapter will trace the diagnostic evolution of this entity in the past five decades.