Leukemia, colloquially known as blood cancer, refers to various types of cancers caused by malignant changes in white blood cells (leukocytes) in the bone marrow or lymphatic system. As a result, blood formation is disturbed and an increasing number of non-functional leukocytes are formed, which displace the healthy blood cells. In Germany, more than 11,400 people contract leukemia each year – from young children to the elderly, anyone can be affected.
What 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)
In addition, a whole range of related forms exists. The demarcation of chronic forms of leukemia to the “non-Hodgkin’s lymphoma“, various forms of malignant lymph node cancer, is fluid.
Leukemia: causes and risk factors.
To date, it is not clear exactly what causes blood cancer. However, some risk factors are known or suspected to increase the risk for certain forms of leukemia:
- Ionizing radiation
- Drugs or chemicals (e.g., cytostatics as anticancer agents for chemotherapy, benzene).
- Certain viruses (e.g. Human T-cell Leukemia Virus = HTLV, a relative of HIV, the AIDS pathogen).
- Genetic predisposition (e.g. twin siblings fall ill more often; in CML – chronic myeloid leukemia – often the “Philadelphia chromosome” can 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, the blood-forming organs, the various blood cells are produced from common precursor cells, the stem cells, through several stages of maturation:
- Red blood cells (erythrocytes) for the transport of oxygen and carbon dioxide.
- White blood cells (leukocytes) for immune defense
- Blood platelets (thrombocytes) for blood clotting
Leukocytes are divided into three subgroups:
- Granulocytes
- Lymphocytes
- Monocytes
What happens in the body during leukemia?
The three subgroups of white blood cells have different tasks and are newly produced and released into the circulating blood in the healthy body in the exact amount in which they perish. This finely balanced mechanism requires some steering and control functions. Among other things, there are inhibitory mechanisms that prevent overproduction. In the various forms of leukemia, this inhibitory function is now disturbed and malignant cells can divide unhindered. Unlike healthy cells, however, these leukocytes do not develop to the point where they can perform their normal function. Instead, immature precursors of leukocytes are released into the blood, also known as blasts. Due to their enormous numbers, these displace normal hematopoiesis in the bone marrow, leading to the typical symptoms. The quantity of these cells can be so large that the patient’s blood appears whitish instead of red – hence the name leukemia (= white blood).
Why are there different types of leukemia?
Different types of blood cancers are distinguished based on several criteria:
- Depending on which cell type is affected, a distinction is made between myeloid and lymphoid leukemias. These are further subdivided into individual forms by means of microscopic, cytochemical (e.g. cell staining) and immunological examinations.
- Depending on how mature the cells formed, one divides into mature cell and immature cell leukemias.
- Depending on the number of leukocytes 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 blood, so they quickly become fatal without therapy. On the other hand, they are more curable with treatment. Acute leukemia can occur even in children.In the chronic forms, on the other hand, mainly mature cells are found in the blood. The chronic forms of blood cancer progress insidiously and often over years to decades, so they are often discovered only by chance. A cure is often not possible. Chronic leukemia occurs primarily in middle and late adulthood.
