The World Health Organisation (WHO) classification of lymphoid neoplasms (p195) has refined the Revised European American Lymphoma (REAL) classification producing a list of clinico-pathologically well characterised lymphomas using morphology, immunophenotype, genotype, the normal cell counterpart and clinical behaviour. Inter- and intraobserver reproducibility is 85-95%. In Europe and the USA 85% of lymphomas are B-cell type.

The clinical behaviour of lymphomas informs management strategies in clinical practice and current treatment protocols are still based on classification systems that group histological diagnoses into indolent (low grade) and aggressive (intermediate and high grade or simply high grade) NHL. More biologically relevant classification of lymphoma diagnosis using the WHO system and emerging therapeutic options based on immunological and molecular characteristics may increase the diagnosis-specific nature of therapy in the future.

WHO classification of lymphoid neoplasms

B-cell neoplasms Precursor B-cell neoplasms

• Precursor B-lymphoblastic leukaemia/lymphoma (precursor B-cell acute lymphoblastic leukaemia)

Mature (peripheral B-cell) neoplasms

• Chronic lymphocytic leukaemia/B-cell small lymphocytic lymphoma 2 B-cell prolymphocyte leukaemia

• Lymphoplasmacytic lymphoma

• Splenic marginal zone B-cell lymphoma (splenic lymphoma with villous lymphocytes)

• Hairy cell leukaemia

2 Plasma cell myeloma/plasmacytoma

• Extranodal marginal zone B-cell lymphoma (MALT lymphoma)

• Nodal marginal zone B-cell lymphoma

• Follicular lymphoma

• Mantle cell lymphoma

• Diffuse large B-cell lymphomas

• Burkitt lymphoma/leukaemia

T-cell neoplasms Precursor T-cell neoplasms

• Precursor T-lymphoblastic leukaemia/lymphoma (precursor T-cell acute lymphoblastic leukaemia)

• Blastoid NK-cell lymphoma Mature (peripheral) T-cell neoplasms

• T-cell prolymphocytic leukaemia

• T-cell large granular lymphocytic leukaemia

• Aggressive NK-cell leukaemia

• Adult T-cell leukaemia/lymphoma

• Extranodal NK/T-cell lymphoma (nasal type)

• Enteropathy type T-cell lymphoma

• Hepatosplenic T-cell lymphoma

• Subcutaneous panniculitis-like T-cell lymphoma

• Mycosis fungoides/Sezary syndrome

• Primary cutaneous anaplastic large cell lymphoma

• Peripheral T-cell lymphoma (not otherwise specified)

• Angioimmunoblastic T-cell lymphoma

• Primary systemic anaplastic large cell lymphoma

Hodgkin lymphoma

• Nodular lymphocyte predominant Hodgkin lymphoma

• Classical Hodgkin lymphoma

- Nodular sclerosis Hodgkin lymphoma (Grades 1 & 2)

- Lymphocyte-rich classical Hodgkin lymphoma

- Mixed cellularity Hodgkin lymphoma

- Lymphocyte depleted Hodgkin lymphoma

Harris, N.L. et al. (1994) A revised European-American classification of lymphoid neoplasms: a proposal from the International Lymphoma Study Group. Blood, 84, 1361-1392; Jaffe ES et al (2001). in Kleihues P, Sobin L eds. WHO Classification of Tumours. Lyon: ARC Press.

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