Leukemia (blood cancer) - causes and development

Leukemia, also known as blood cancer, refers to various types of cancers caused by malignant changes in the white blood cells (leukocytes) in the bone marrow or lymphatic system. As a result, the formation of blood is disturbed and it is increasingly non-functional leukocytes are formed, which displace the healthy blood cells. In Germany, more than 11, 400 people suffer from leukemia every year - from small children to old people, anyone can be affected.

Which types of leukemia are there?

Different types of leukemia are distinguished. The most important are:

  • acute lymphoblastic leukemia (ALL)
  • acute myeloid leukemia (AML)
  • chronic lymphocytic leukemia (CLL)
  • chronic myeloid leukemia (CML)

There are also a number of related forms. The delineation of the chronic forms of leukemia to the "non-Hodgkin's lymphoma", so different forms of malignant lymph node cancer, is fluid.

Leukemia: causes and risk factors

To date, it is still not clear exactly what the causes of blood cancer are. However, some risk factors are known or suspected to increase the risk of certain forms of leukemia:

  • Ionizing radiation
  • Medicines or chemicals (eg cytostatics as a cancer treatment for chemotherapy, benzene)
  • Certain viruses (eg Human T-cell Leukemia Virus = HTLV, a relative of HIV, the AIDS pathogen)
  • Genetic predisposition (for example, twin siblings are more likely to become ill, in CML - chronic myeloid leukemia - the "Philadelphia chromosome" can often be found)

How does blood formation work?

To understand what leukemia is, it helps to first look at the processes involved in hematopoiesis. In the bone marrow and lymphatic system, ie the blood-forming organs, the different blood cells are produced from common precursor cells, the stem cells, via several stages of maturation:

  • red blood cells (erythrocytes) for the transport of oxygen and carbon dioxide
  • white blood cells (leukocytes) for the immune defense
  • Platelets (platelets) for blood clotting

The leukocytes are subdivided into three subgroups:

  • granulocytes
  • lymphocytes
  • monocytes

What happens with leukemia in the body?

The three subgroups of white blood cells have different roles and are re-produced in the healthy body in exactly the same amount and released into the circulating blood in which they perish. This finely balanced mechanism requires some control and monitoring functions. Among other things, there are inhibitory mechanisms that prevent overproduction.

In the various forms of leukemia now this inhibitory function is disturbed and malignant cells can divide unhindered. Unlike healthy cells, however, these leukocytes do not develop enough to function normally.

Instead, immature precursors of leukocytes are released into the blood, which are also called blasts. These displace the normal blood formation in the bone marrow by their enormous number, which leads to the typical symptoms. The amount of these cells can be so large that the blood of patients appears whitish instead of red - hence the name leukemia (= white blood).

Why are there different leukemia types?

The differentiation of the different types of blood cancer is based on various criteria:

  • Depending on which cell type is affected, a distinction is made between myeloid and lymphatic leukemias. These are subdivided further into individual forms by means of microscopic, cytochemical (eg cell staining) and immunological investigations.
  • Depending on how mature the cells are, it is divided into mature-cell and immature-cell leukemias.
  • Depending on the leukocyte count in the blood one speaks of a subleukemic or aleukemic (normal or reduced number) or leukemic form (number increased).
  • Depending on the clinical course, acute and chronic forms can be distinguished.

Acute and chronic leukemia: differences

The acute forms of leukemia are characterized by the release of many immature cells into the bloodstream so that they become fatal without therapy. On the other hand, they are better curable by a treatment. Acute leukemia can already occur in children.

In the case of chronic forms, on the other hand, mature cells are found in the blood. The chronic forms of blood cancer are creeping and often over years to decades, so they are often discovered only by accident. A cure often impossible. Chronic leukemia occurs mainly in middle and late adulthood.

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