Non-Hodgkin Lymphoma

Non-Hodgkin lymphoma is a large and heterogeneous group of malignancies arising from B lymphocytes, T lymphocytes, or natural killer cells. Defined historically by exclusion of Hodgkin lymphoma, it ranges from indolent disorders compatible with long survival to rapidly progressive aggressive lymphomas. Modern classification groups its many entities by cell of origin, morphology, immunophenotype, and molecular genetics rather than by a single unifying feature.

Definition

Non-Hodgkin lymphoma is any of a large set of lymphoid malignancies derived from B, T, or NK cells that lack the defining features of Hodgkin lymphoma, classified into distinct entities by lineage, differentiation stage, morphology, immunophenotype, and genetics.

Scope

This entry frames non-Hodgkin lymphoma as the diverse remainder of lymphoid neoplasms outside Hodgkin lymphoma, introduces its division into indolent and aggressive categories, names representative entities such as diffuse large B-cell lymphoma and follicular lymphoma, and describes the classification and staging logic that organises the group. It is a reference description and not management guidance.

Core questions

• How is non-Hodgkin lymphoma distinguished from Hodgkin lymphoma?
• What separates indolent from aggressive non-Hodgkin lymphomas?
• How are the many entities defined by cell of origin and molecular features?
• How is disease extent described and assessed?

Key concepts

• Cell of origin (B-cell, T-cell, NK-cell)
• Indolent versus aggressive lymphoma
• Diffuse large B-cell lymphoma
• Follicular lymphoma
• Immunophenotype and molecular classification
• Lugano staging and response assessment
• Germinal-centre and post-germinal-centre origin

Mechanisms

Non-Hodgkin lymphomas arise when a lymphocyte at a particular differentiation stage acquires genetic alterations that drive clonal proliferation and survival; the resulting neoplasm reflects its normal-counterpart cell of origin, which is why immunophenotype and molecular profile define each entity. Indolent lymphomas such as follicular lymphoma typically proliferate slowly and pursue a protracted course, whereas aggressive lymphomas such as diffuse large B-cell lymphoma grow rapidly. Successive World Health Organization classifications, including the 2016 revision and the 2022 fifth edition, integrate morphology, immunophenotype, and recurrent genetic lesions to define the entities, and the Lugano classification standardises how extent and treatment response are described.

Clinical relevance

Non-Hodgkin lymphoma illustrates how a single historical label conceals great biological diversity, and understanding its classification clarifies why prognosis varies so widely across subtypes. As a reference topic it organises a major part of hemato-oncology. This entry describes the disease group conceptually and is not a basis for individual diagnosis or treatment.

Epidemiology

Non-Hodgkin lymphoma is considerably more common than Hodgkin lymphoma and is among the more frequent malignancies worldwide, with incidence generally rising with age. B-cell lymphomas predominate, with diffuse large B-cell lymphoma the most common aggressive entity and follicular lymphoma a leading indolent entity; T-cell and NK-cell lymphomas are less common and vary by region.

History

The category took shape as classifications sought to order the many lymphomas that were not Hodgkin lymphoma. Successive schemes, from the Revised European-American Lymphoma classification to the World Health Organization classifications, replaced earlier morphology-based systems with entities defined by cell of origin and molecular features, a process continued in the 2016 revision and the 2022 fifth edition.

Debates

Molecular subclassification of diffuse large B-cell lymphoma

Gene-expression and genetic studies divide diffuse large B-cell lymphoma into cell-of-origin and molecular subgroups, and how best to incorporate these distinctions into a practical classification continues to be refined.

Key figures

• Steven H. Swerdlow
• Laurie H. Sehn
• Bruce D. Cheson

Seminal works

• swerdlow-2016
• alaggio-2022
• sehn-2021

Frequently asked questions

What does 'non-Hodgkin' mean?

It is a historical label for the many lymphoid malignancies that lack the defining Reed-Sternberg cells and other features of Hodgkin lymphoma. The term groups biologically diverse diseases that are now classified individually by cell of origin and molecular features.

What is the difference between indolent and aggressive non-Hodgkin lymphoma?

Indolent lymphomas, such as follicular lymphoma, generally grow slowly and follow a prolonged course, whereas aggressive lymphomas, such as diffuse large B-cell lymphoma, proliferate rapidly. The distinction reflects underlying biology and shapes how each entity is understood.