Classification of hematopoietic and lymphoid tissue tumors. WHO
Work began in 1995. Initially, it was carried out by 10 national committees, which included more than 50 leading pathologists in the world. The classification is based on the same principles that were used as the basis for the REAL classification of lymphomas (Revised European-American Classification of Lymphoid Neoplasms): morphological (histological and cytological) studies, immunophenotyping, cytogenetic research and analysis of clinical data are necessary to establish the diagnosis. Thus, when creating the classification, the authors were based on the biological features of the tumor determined by modern methods.
As soon as the classification was formulated by pathologists, a committee was created to verify its clinical value, which included more than 40 leading oncologists and hematologists in the world. After their work in 1997 at a special meeting of clinicians and pathologists, all the disputed clinical issues were discussed and agreed upon. Only after an agreement was reached at this meeting, was the WHO classification finalized and published.
Thus, as a result of the involvement of many specialists in most countries, the WHO classification has become the first classification of hematological tumors that is currently accepted and used throughout the world. Nevertheless, there are controversial issues in the classification. In all likelihood, it will still be refined and changed.
In the WHO classification, all hematological neoplasms are divided into groups according to the blood line to which the cells constitute the morphological substrate of this tumor: tumors from myeloid cells, lymphoid cells, histiocytic / dendritic cells (histiocytosis) and mast cells (mastocytosis).
Tumors from lymphoid cells in accordance with this classification are discussed in detail in the manual, but here is the view of one of the well-known immunologists, prof. N. N. Tupitsyn on the value of this classification. At the same time, the section on tumors of myeloid cells, in our opinion, should be considered.
Tumors from myeloid cells are divided into 4 large groups:
1) chronic myeloproliferative diseases;
2) diseases that have features of both myeloproliferative diseases and myelodysplasias;
3) myelodysplastic syndromes;
4) acute myeloid leukemia.