Malignant proliferative diseases are the most important white cell disorders. By origin of the tumor cells and their biological properties hematopoietic cells tumors can be divided into three groups.
Classification of the hematopoietic cells malignancies.
• Non-Hodgkin lymphoid neoplasms.
- Precursor B- and T-cell lymphoblastic leukemias (correspond to normal pre-Band pre-T-cells; originate in the bone marrow).
- Malignant lymphomas (reside predominantly in lymphoid tissue, resemble solid tumors).
• Hodgkin lymphoid neoplasms.
• Myeloid neoplasms (arise in hematopoietic stem cells that give rise to cells of the myeloid lineage).
Causes of the hematopoietic cell malignancies.
• Inherited genetic factors (Fanconi anemia, ataxia-telangiectasia, the Down syndrome).
• Chemical agents (benzene, smoking, petroleum products, herbicides, pesticides).
• Viruses (human T-lymphocyte leukemia virus I (HTLV-I), Epstein-Barr virus, human herpes virus 8).
• Physical factors (ionizing radiation).
• Iatrogenic factors (radiotherapy, certain forms of chemotherapy).
• Chromosome translocations and oncogenes.
Characteristics of atypia of growth of leukemic cells are described in fig. 21.
General characteristics of leukemia.
• Atypism.
• Coexistence of two lines of hematopoietic cells of the same type: normal and malignant.
• The malignant line is characterized by impairment of differentiation and is presented by blasts and immature precursors.
• The normal population of cells is crowded out.
• Leukemic reaction in the peripheral blood.
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Fig. 21. Atypia of growth in leukemia
Classification of the leukemic reaction in the peripheral blood based on leukocyte counts and the presence of the blast forms includes the following groups.