Chapter 20: Non-Hodgkin Lymphomas

Unlike other lymphatic cancers, NHL displays an irregular spread and frequently involves extranodal sites such as the gastrointestinal tract, skin, and central nervous system. A fundamental clinical distinction is made between low-grade and high-grade diseases; low-grade lymphomas are typically indolent and slowly progressive but difficult to cure entirely, whereas high-grade lymphomas are aggressive and require urgent treatment but possess a higher potential for complete eradication. Diagnostic procedures emphasize the necessity of tissue biopsies over fine-needle aspirations to preserve architectural details, supplemented by immunophenotyping to confirm cellular clonality and genetic analysis to identify hallmark chromosomal translocations. The text details various B-cell subtypes, including small lymphocytic lymphoma and lymphoplasmacytoid lymphoma, which is often associated with Waldenström macroglobulinaemia and its associated hyperviscosity symptoms. It also explores marginal zone lymphomas, specifically the mucosa-associated lymphoid tissue (MALT) variant linked to chronic infections like Helicobacter pylori. Follicular lymphoma is identified as a common subtype characterized by the t(14;18) translocation and BCL2 overexpression. Transitioning to high-grade entities, the chapter focuses on mantle cell lymphoma and diffuse large B-cell lymphoma (DLBCL), the latter being the most prevalent high-grade form. Additionally, Burkitt lymphoma is highlighted for its extreme proliferative index and its association with Epstein-Barr virus in endemic cases. Furthermore, the chapter addresses T-cell and NK-cell lymphomas, including cutaneous forms like mycosis fungoides and Sézary syndrome, as well as anaplastic large cell lymphoma. Treatment methodologies have evolved significantly, now incorporating monoclonal antibodies such as rituximab, targeted inhibitors that block specific signalling pathways like BTK and PI3K, and advanced chimeric antigen receptor (CAR)-T cell therapies for patients with resistant disease. Prognostic tools like the International Prognostic Index (IPI) and imaging technologies like PET/CT scans are established as vital components for staging and monitoring therapeutic efficacy.