WHO classification of lymphoid malignancies

Gluzman D.F.

R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology,National Academy of Sciences of Ukraine

Correspondence: gluzman@onconet.kiev.ua

Lymphoid malignancies are tumors of the immune system that originate from B or T lymphocytes and, rarely, from NK cells. They encompass extremely heterogeneous group of diseases based on their histological forms, biologic and molecular genetic features, sites of clinical presentation (nodal or extranodal), tumor behavior (localized or disseminated), and response to the treatment.

The history of recognition and classification of lymphoid malignancies is long, controversial and complicated. Two classification systems have been widely used until recently, the Kiel classification of non-Hodgkin’s lymphomas and the Working Formulation for clinical usage. In 1994 after the immunologic revolution (creation the hybridoma technology that led to the development of monoclonal antibodies) and dramatic progress in understanding the genetics of lymphoid malignancies), the International Lymphoma Study Group (ILSG) of experienced hematologists formulated new proposals for a modern lymphoma classification, the so-called Revised European American Lymphoma (REAL) classification. With some additions and corrections, it has been developed into World Health Organization (2001) classification (E.S. Jaffe, N.L. Harris, H. Stein, J.W. Vardiman, eds. Pathology and Genetics of Tumours of Haematopoietic and Lymphoid Tissues. Lyon: IARC Press, 2001. 351 p.).

The 4th edition of the WHO classification of Tumours of Haematopoietic and Lymphoid Tissues (2008) incorporates new information that has emerged from basic and clinical investigations and includes new defining criteria for some diseases as well as number of new entities defined by a combination of immunophenotype, genetic criteria and clinical features.

The recent WHO classification (2008) has been updated as a joint effort of more than 130 hemopathogists from 22 countries. WHO classification of the B cell, T cell and NK cell neoplasms that in many respects recapitulate normal stage of lymphoid cell differentiation subdividing tumors into those with an immature or blastic appearance versus more mature stage of lymphoid development. This classification system represents a significant advance in our ability to understand, identify and treat different lymphoma entities. It is based on the concept of clinicopathologic entities in which histology, immunophenotype, molecular genetic data as well as clinical features are integrated. The putative cell origin and stage of differentiation of different types of lymphoid malignancies is also taken into account.

According to our experience, the application of immunocytochemical and molecular genetic studies has led to the detection of small number of pathologic cells in peripheral blood and bone marrow of some patients with non-Hodgkin’s lymphomas.

In 1993, the Reference Laboratory was set up as a public service on the basis of the Immunocytochemistry Department of R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobio­logy, National Academy of Sciences of Ukraine with the aim of the precise diagnosis of the haematopoietic malignancies based on cytomorphology, cytoche­mistry, immunophenotyping and the techniques of molecular biology in accordance with FAB, WHO, EGIL, ICD-10 and ICD-O-2 classifications. The diagnostic activity of the Reference Laboratory covers 35-45% of all Ukrainian patients with acute leukemias, chronic lymphoid and myeloid leukemias, myelodysplastic syndromes, malignant lymphomas, histiocytosis, and metastatic lesions of lymph nodes and bone marrow. At present, the patients with tumors of haematopoietic and lymphoid tissues are diagnosed according to up-to-date WHO classification. We believe that only precise diagnosis of the major types of hematological malignancies to the up-to-date classification with delineation of the specific biological subtypes of hematological malignancies may represent the basis for further molecular biological and epidemiological studies. New insight into the biology of the lymphoid malignancies in the coming years might well improve our ability to evaluate patients and chose therapy.

References

1. Ferry YA, Harris NL. Atlas of lymphoid hyperplasia and lymphoma. Philadelphia: W.B. Saunders Co., 1997. 273 p.

2. Human lymphoma: clinical implications of the REAL classification. D.Y. Mason, N.L. Harris (eds.). London etc.: Springer-Verlag, 1999. 554 p.

3. World Health Organization classification of tumours. Pathology and genetics of tumours of haematopoietic and lymphoid tissues. E.S. Jaffe, N.L. Harris, H. Stein, Y.W. Vardiman (eds.). Lyon: IARC Press, 2001. 351 p.

4. Feller AC, Diebold J. Histopathology of nodal and extranodal non-Hodgkin lymphoma. Berlin etc.: Springer-Verlag, 2004. 464 p.

5. The lymphomas, 2nd ed. G.P. Canellos T.A. Lister, B. Young (eds). Philadelphia: Elsevier Inc., 2006. 581 p.

6. WHO classification of tumours of haematopoietic and lymphoid tissues. S.H. Swerdlow, E. Campo, N.L. Harris, E.S. Jaffe, S.A. Pileri, H. Stein, J. Thiele, J.W. Vardiman (eds.). Lyon: IARC Press, 2008. 439 p.

7. Gluzman DF, Sklyarenko LM, Nadgornaya VA. Tumours of haematopoietic and lymphoid tissues (cytomorphology, immunocytochemistry, diagnostic algorithms). Kyiv: DIA, 2008. 193 p. (in Russian)

8. Gluzman DF, Sklyarenko LM, Nadgornaya VA. Diagnostic oncohaematology. Kyiv: DIA, 2011. 256 p. (in Russian).

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