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Since 2022 there have been two reference classifications of lymphoma rather than one, published within months of each other by overlapping groups of experts. They agree about most diseases and disagree about a handful of names and boundaries, so the same biopsy can carry two different diagnoses depending on which book the pathologist used.
The fifth edition of the WHO Classification of Haematolymphoid Tumours (WHO-HAEM5) and the International Consensus Classification of Mature Lymphoid Neoplasms (ICC) were both published in 2022. WHO-HAEM5 arranges diseases in a hierarchy of class, family and entity, and orders the entities within a family from the most indolent to the most aggressive. The ICC was produced by a Clinical Advisory Committee convened around the same evidence.
The disagreements that change what a patient is called:
Nodular lymphocyte predominant Hodgkin lymphoma. The ICC renamed it nodular lymphocyte predominant B-cell lymphoma by consensus, on the grounds that it differs biologically and clinically from classic Hodgkin lymphoma and is closely related to T-cell/histiocyte-rich large B-cell lymphoma. WHO-HAEM5 kept the old name, explicitly so as not to interfere with trials already recruiting, while stating that the new name is acceptable in preparation for adopting it later.
High-grade B-cell lymphoma with MYC and BCL6 rearrangements. Both books removed these cases from the double-hit category defined by MYC and BCL2. WHO-HAEM5 reassigns them to diffuse large B-cell lymphoma or high-grade B-cell lymphoma not otherwise specified according to how the cells look. The ICC created a new provisional entity for them instead.
The double-hit entity itself. WHO-HAEM5 names it diffuse large B-cell lymphoma / high-grade B-cell lymphoma with MYC and BCL2 rearrangements, so that a tumour made of large cells and a tumour made of blastoid cells can carry the same name once the genetics are known. The ICC keeps high-grade B-cell lymphoma with MYC and BCL2 rearrangements as the name and asks that the appearance be reported alongside.
Extranodal NK/T-cell lymphoma. WHO-HAEM5 dropped the qualifier nasal type, because the disease occurs at several extranodal sites. The ICC retains it.
Lymphomas of immune-privileged sites. WHO-HAEM5 created a single entity grouping primary large B-cell lymphoma of the central nervous system, of the vitreoretina and of the testis. The ICC discussed the same grouping and decided it was premature, while recognising primary diffuse large B-cell lymphoma of the testis as an entity in its own right.
Primary cutaneous marginal zone disease. WHO-HAEM5 made it a separate entity and calls it a lymphoma. The ICC made it a separate entity and calls it a lymphoproliferative disorder, which is a statement about how dangerous it is rather than about what it is.
The nodal T-follicular helper cell lymphomas. WHO-HAEM5 names the family nodal T-follicular helper cell lymphoma, with the angioimmunoblastic type as the prototype. The ICC calls the same family follicular helper T-cell lymphoma. Both replace the older name angioimmunoblastic T-cell lymphoma with a longer one.
What a reader should do with this. If a report, a second opinion and a trial protocol give three names, they are probably describing one disease in three vocabularies, and asking which classification each used is a reasonable question to put to the haematologist.
Leukaemias, myeloma and MDS live in the marrow and blood; lymphomas grow in lymph nodes and spleen. The node stations are the disease map, not a route of spread, and staging counts them.
In lymphoma the node stations are the disease itself; staging (Ann Arbor / Lugano) counts how many regions and sides of the diaphragm are involved.
Same organ: High-grade B-cell lymphoma with MYC and BCL2 rearrangements (double-hit lymphoma), Mediastinal grey zone lymphoma, Primary effusion lymphoma, Plasmablastic lymphoma, T-cell/histiocyte-rich large B-cell lymphoma, EBV-positive diffuse large B-cell lymphoma, Primary large B-cell lymphoma of the testis, Gastric MALT lymphoma, Ocular adnexal MALT lymphoma, Extranodal NK/T-cell lymphoma, Adult T-cell leukaemia/lymphoma, ALK-positive anaplastic large cell lymphoma, ALK-negative anaplastic large cell lymphoma, Breast implant-associated anaplastic large cell lymphoma, Primary cutaneous anaplastic large cell lymphoma, Lymphomatoid papulosis, Mycosis fungoides, Enteropathy-associated T-cell lymphoma, Monomorphic epitheliotropic intestinal T-cell lymphoma, Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), Splenic marginal zone lymphoma, Nodal marginal zone lymphoma, Primary cutaneous marginal zone lymphoma, Primary cutaneous follicle centre lymphoma, Sezary syndrome, Nodal T-follicular helper cell lymphoma, angioimmunoblastic type (angioimmunoblastic T-cell lymphoma), Hepatosplenic T-cell lymphoma, Intravascular large B-cell lymphoma, Lymphomatoid granulomatosis, T-cell prolymphocytic leukaemia, Splenic B-cell lymphoma/leukaemia with prominent nucleoli (formerly B-cell prolymphocytic leukaemia and hairy cell leukaemia variant), T-cell large granular lymphocytic leukaemia, Mixed-phenotype acute leukaemia, Myeloid leukaemia of Down syndrome, Burkitt leukaemia, Marginal zone lymphoma, Cutaneous T-cell lymphoma (mycosis fungoides and Sezary syndrome), Primary mediastinal (thymic) large B-cell lymphoma, Leukaemia (all types), Acute myeloid leukaemia, Acute lymphoblastic leukaemia, Chronic lymphocytic leukaemia, Chronic myeloid leukaemia (CML), Diffuse large B-cell lymphoma, Follicular lymphoma, Hodgkin lymphoma, Mantle cell lymphoma, Multiple myeloma, Myelodysplastic syndromes / neoplasms (MDS), Myeloproliferative neoplasms (PV, ET, myelofibrosis), Polycythaemia vera (PV), Essential thrombocythaemia (ET), Waldenström macroglobulinaemia, Hairy cell leukaemia, Peripheral T-cell lymphomas (including cutaneous T-cell lymphoma), Blastic plasmacytoid dendritic cell neoplasm (BPDCN), Burkitt lymphoma, HIV-associated (AIDS-related) lymphomas, Chronic myelomonocytic leukaemia and MDS/MPN overlap neoplasms, Systemic mastocytosis, Erdheim-Chester disease, Rosai-Dorfman disease and other histiocytic neoplasms, Langerhans cell histiocytosis (LCH), Post-transplant lymphoproliferative disorder (PTLD), FLT3-mutated acute myeloid leukaemia, IDH1- and IDH2-mutated acute myeloid leukaemia, NPM1-mutated and KMT2A-rearranged acute myeloid leukaemia, Secondary and therapy-related acute myeloid leukaemia, Acute promyelocytic leukaemia, Acute myeloid leukaemia in older or unfit patients, Smouldering multiple myeloma, Newly diagnosed multiple myeloma, transplant-eligible, Newly diagnosed multiple myeloma, transplant-ineligible, Relapsed or refractory multiple myeloma, Plasma cell leukaemia, Lower-risk myelodysplastic syndromes, Higher-risk myelodysplastic syndromes, Chronic lymphocytic leukaemia, first treatment, Relapsed or refractory chronic lymphocytic leukaemia, Richter transformation of chronic lymphocytic leukaemia, Chronic myeloid leukaemia, chronic phase, Chronic myeloid leukaemia, accelerated and blast phase, Primary myelofibrosis, Standard-risk B-cell acute lymphoblastic leukaemia in children, High-risk acute lymphoblastic leukaemia in children (high-risk B-ALL and T-ALL), Philadelphia chromosome-positive acute lymphoblastic leukaemia in children (Ph-positive ALL), Philadelphia chromosome-like acute lymphoblastic leukaemia (Ph-like or BCR::ABL1-like ALL), Infant acute lymphoblastic leukaemia (KMT2A-rearranged, under one year), Relapsed and refractory acute lymphoblastic leukaemia in children, Acute myeloid leukaemia in children, Erdheim-Chester disease, Rosai-Dorfman-Destombes disease, Single-system Langerhans cell histiocytosis (bone, skin or one other organ), Multisystem Langerhans cell histiocytosis (with or without risk-organ involvement), Indolent and smouldering systemic mastocytosis, Advanced systemic mastocytosis (aggressive SM, SM with an associated haematological neoplasm, mast cell leukaemia), Early-stage classical Hodgkin lymphoma (stage I to II), Advanced-stage classical Hodgkin lymphoma (stage III to IV), Nodular lymphocyte-predominant Hodgkin lymphoma (nodular lymphocyte-predominant B-cell lymphoma), Relapsed and refractory classical Hodgkin lymphoma
Showing the organ this term concerns: Non-Hodgkin lymphoma (all types).
Shares Breast implant-associated anaplastic large cell lymphoma, Lymphomatoid papulosis, Primary effusion lymphoma, Enteropathy-associated T-cell lymphoma and the tags heme, lymphoma.
Shares Enteropathy-associated T-cell lymphoma, Monomorphic epitheliotropic intestinal T-cell lymphoma, ALK-negative anaplastic large cell lymphoma, ALK-positive anaplastic large cell lymphoma and the tags heme, lymphoma.
Shares Indolent and aggressive lymphoma, Gastric MALT lymphoma, Mycosis fungoides, Diffuse large B-cell lymphoma and the tags heme, lymphoma.
Shares Enteropathy-associated T-cell lymphoma, Gastric MALT lymphoma, Monomorphic epitheliotropic intestinal T-cell lymphoma, Non-Hodgkin lymphoma (all types) and the tags heme, lymphoma.
Shares Adult T-cell leukaemia/lymphoma, Lymphoma (tissue type), Peripheral T-cell lymphomas (including cutaneous T-cell lymphoma), Non-Hodgkin lymphoma (all types) and the tags heme, lymphoma.
Shares Indolent and aggressive lymphoma, Gastric MALT lymphoma, Non-Hodgkin lymphoma (all types) and the tags heme, lymphoma.
Shares Primary effusion lymphoma, T-cell/histiocyte-rich large B-cell lymphoma, EBV-positive diffuse large B-cell lymphoma, High-grade B-cell lymphoma with MYC and BCL2 rearrangements (double-hit lymphoma).
Shares Lymphoma (tissue type), Non-Hodgkin lymphoma (all types) and the tag heme.