Leukemia is a form of cancer that affects the blood or blood making tissues. Bone marrow is found in the spongy regions of the bones, usually pelvis bones, sternum, vertebrae, and ribs. It is tasked with making early blood-forming cells, white blood cells, platelets, and the precursors of red blood cells. These precursors grow until they mature in the bone marrow and then released into the bloodstream.
Well, blood cancer develops when the bone marrow forms unusual blood cells, which start to divide out of control. More often than not, this form of cancer affects the white blood cells, but it can affect other types of blood cells too. White blood cells play a significant role in fighting infections in the body, but when leukemia affects them, they become leukemia cells, and they fail to die like normal cells. Instead, they garner and crowd out the normal cells. This includes normal white blood cells, platelets, and red blood cells, as well as their precursors found in the bone marrow. This, as you can expect, leads to an array of problems, including easy bruising and bleeding, failure to get adequate oxygen to body tissues, and an increased risk of infections.
Leukemia cells, over time, can spread through the bloodstream and blood, sometimes referred to as a liquid tumor. This is where they divide, occasionally forming solid tumors and also doing damage to body organs. Which organs sustain damage depends on the type of blood cancer. For instance, the liver, lymph nodes, and spleen may become swollen and enlarged as a result of the accumulation of the abnormal cells. In other cases, leukemia cells reach the CNS (or central nervous system) and garner in the cerebrospinal fluid.
In the U.S alone, almost 50,000 people are diagnosed with leukemia each year, and over 23,000 die of the condition. This type of cancer usually affects adults older than 55 years, but it is also the most common form of cancer in teens and children younger than 15. The cause of this condition is not well known, but exposure to cancer-causing chemicals, radiation, and anticancer drugs have been seen to increase the risk of developing it. Some cases are due to rare viral infections and genetic disorders in others.
Types of Leukemia
There are several types of blood cancer. Each type is classified based on if it grows rapidly and becomes lethal fast if not treated (this is also referred to as acute blood cancer), or grows gradually (or chronic blood cancer) and also the type of white blood cell that cancer started.
There are two categories of early blood-forming cells that produce white blood cells (or immature precursors):
- Myeloid Precursor Cells: These produce red blood cells and a number of white blood cells called granulocytes. The latter move in the bloodstream fighting infections through killing and digesting the harmful bacteria.
- Lymphoid Precursor Cells: These grow and mature into lymphocytes, a kind of white blood cell that can be found in both the lymphatic and blood circulatory system. Their role is to coordinate your body’s immune response, and a huge number of them produce antibodies.
As such, blood cancer can be classified as Lymphoid or Myeloid. There is another type of cancer that affects the lymphocytes, but it does not occur in the bone marrow, but the lymphatic system instead. It is referred to as lymphoma, and it is diagnosed and treated rather differently.
The Four Primary Leukemia Categories Are:
- ALL (or Acute Lymphocytic Leukemia) – This type of cancer tends to develop from lymphocytes yet to mature. Lymphoid leukemia cells found in acute lymphocytic leukemia are known as leukemic lymphoblasts. This form of cancer can develop quickly, and when not attended to, it can be lethal in just a few months. The cancer cells build up in the blood and bone marrow. Cancer can ideally spread to the lymph nodes and, ultimately, CNS.
One form of acute lymphocytic leukemia is caused by two chromosome pieces breaking and switching places, referred to as translocation. This leads to an altered, fused gene on chromosome 22, referred to as the Philadelphia chromosome. This gene makes a protein that functions abnormally, leading to the overproduction of immature lymphoid cells. This form of cancer is referred to as Philadelphia chromosome-positive acute lymphocytic leukemia.
Untreated acute lymphocytic leukemia can result in poor immunity, easy bleeding and bruising as well as anemia. The condition is common in children compared to adults.
- CLL (or Chronic Lymphocytic Leukemia) – This form of cancer starts in immature lymphocytes, but the leukemic cells occur in mature lymphocytes. Compared to other forms of leukemia, it grows gradually and doesn’t call for frequent treatment. It can remain stable for years, but there’s a faster-developing form of chronic lymphocytic leukemia that tend s to block normal cell production and calls for treatment. Individuals with this form of cancer have enlarged lymph nodes, known as lymphadenopathy, autoimmunity like autoimmune hemolysis, immunoglobulin deficiencies that result in poor immunity as well as an enlarged spleen. This condition primarily affects older adults.
- AML (or Acute Myeloid Leukemia) – This is a rapidly growing form of cancer whereby the immature myeloid cells divide continually in the bone marrow and can replace it with immature and abnormal white blood cells. When this form of cancer is untreated, it can result in poor immunity, infections, anemia, as well as easy bruising and bleeding. AML is usually common in older adults, but it can ideally occur in young adults and kids. Acute promyelocytic leukemia is a subtype example of AML that’s treated differently from other AML forms and usually has better results.
- CML (or Chronic Myeloid Leukemia) – This is another slowly-developing form of blood cancer. Individuals with CML usually have no symptoms initially but are usually diagnosed during a routine physical or blood test. When symptoms occur, they tend to be similar to common, less serious conditions and include stomach discomfort due to an enlarged spleen, less energy, pale skin and weight loss that’s unaccounted for. Similar to Philadelphia chromosome-positive acute lymphocytic leukemia, CML is caused by an abnormal gene (BCR/ABL) on chromosome 22. If left unattended, CML can result in poor immunity, anemia, overly enlarged spleen, and excessive bruising and bleeding. The condition is prevalent in adults, with seniors over 65 experiencing a higher risk. CML rarely affects younger adults and children, and it can be treated with drugs known as tyrosine kinase inhibitors.
The Signs and Symptoms of Leukemia
Blood cancer signs and symptoms tend to vary depending on the type. The acute type may cause signs and symptoms related to not having adequate normal blood cells.
The signs and symptoms include:
- Shortness of breath, pale skin, and weakness due to anemia (a lack of red blood cells).
- Fever & infections as a result of inadequate infection-fighting white blood cells.
- Bruising and bleeding as a result of a lack of platelets.
Other signs & symptoms may include headaches, vomiting, seizure and confusion, joint and bone pain, night sweats, unexplained weight loss, and enlarged spleen, kidneys, lymph nodes, and/or testicles.
Chronic leukemia, as mentioned earlier, grows gradually, and so, it may not have early signs and symptoms. It may, however, cause milder forms of the symptoms prevalent in acute blood cancer. Chronic leukemia can be found by chance during routine checkups before even any symptoms are visible. Some cases may need to be monitored for several years before treatment is needed, while others can be more aggressive. If the cancer cells start to divide more rapidly, they can lead to a blast crisis or progression to acute leukemia. This results in the production of just immature cells and worsening the condition.
Symptoms of chronic leukemia include:
- Feeling rundown or tired
- Loss of appetite and unexplained weight loss
- Breath shortness during normal activity
- Discomfort or pain in the upper left side of the stomach. Usually caused by an enlarged spleen.
- Pale skin
- Bruising and bleeding easily
- Night sweats
Leukemia Lab Tests
There are several lab tests that can be used to diagnose blood cancer, determine the type as well as monitor the treatment’s effectiveness. After an effective treatment or remission, testing can also be done to check whether cancer has returned.
The General Blood Tests Include:
These are routine tests that assess the cells circulating in the bloodstream. They count the number of cells and check the maturity as well as the proportion of the varying cells. These blood tests can give the initial indication of blood cancer. Abnormal results, like a reduced number of red blood cells and increased white blood cell count, can be as a result of leukemia but an array of chronic or temporary conditions. However, immature blood cell precursors or blasts are usually not seen in blood, and so, if present, leukemia is most likely present, and a follow-up test will be ordered. The CBC and WBC differential tests are ideally essential in monitoring the effectiveness of treatment and also the detection of recurrence.
This is a test that is usually used to follow up the above tests with abnormal red blood cells, white blood cells, or platelets. It can also be ordered when the CBC results are unclear. In this test, a blood drop is smeared on a microscope slide and assessed for immature cells or cells with abnormal shapes, appearance, or size compared to normal ones.
Bone Marrow Aspiration or Biopsy
If leukemia is suspected, a bone marrow aspiration, biopsy, or both can be conducted in order to take a closer look at the marrow tissues. A specialist (pathologist) examines the sample using a microscope and evaluates the size, appearance, shape, and number of each cell type and also the proportion of mature and immature blood cells. If blood cancer is present, the next step is to determine the type and severity of the condition. This test ideally helps set a baseline for the bone marrow cells, with an attempt to see how well they respond to treatments.
Some select tests usually include:
- Lumbar Puncture (or Spinal Tap) & Cerebrospinal Fluid Analysis – If blood cancer is detected in the bone marrow, a spinal tap can be done in order to help determine if cancer has spread to the cerebrospinal fluid and CNS. If cancer cells are found in the cerebrospinal fluid, additional treatment such as direct injection of a drug into the CSF may be needed.
- Phenotyping or Immunophenotyping by Cytometry Flow – This is a test that can help detect leukemia and also the type.
- Chromosome Analysis or Karyotyping – This is a cytogenetic test used to map the 46 chromosomes in cells, with the aim of detecting changes in size, number, or arrangements associated with leukemia.
- Molecular Testing – The malfunction of cells that control cell growth and development is one of the factors that lead to uncontrolled cancer cell growth. The malfunctions can stem from DNA abnormalities, like mutations. Laboratory tests detect the abnormalities related to some types of blood cancer. These can help guide treatment and determine the cause of the condition and even assess the effectiveness of the treatment.
Fluorescent In Situ Hybridization
This is another cytogenetic test that looks for alterations in chromosomes resulting from genetic variations. This test is more sensitive than chromosome analysis. An abnormal gene segment in this test is made to fluoresce or light up when bound by a particular probe. The test helps diagnose varying types of blood cancer that look similar but have varying genetic abnormalities, thus calling for varying treatments.