An Overview of Leukemia

Leukemia is a general term that refers to several different types of blood cancer. Leukemia may impact individuals very differently, and treatments may be quite different depending on the type of leukemia they have. A person can get leukemia at any age, but among adults, leukemia is most common in those over age 60. Children do not generally develop cancer at the same rates as older adults. However, when children do develop cancer, leukemia is the most common one, accounting for almost one out of three malignancies past infancy into the teen years.

Leukemia cells in the bone marrow can produce abnormal white blood cells.

What Is Leukemia?

Leukemia is a cancer of the blood-forming cells—those cells in the body that continually make your supply of red and white blood cells, as well the platelets that help your blood to clot. The type of leukemia a person has depends partly on the type of blood-forming cell from which the leukemia developed.

Leukemia starts in the bone marrow—the spongy, inner portion of certain bones where the blood-forming cells are found in abundance. Leukemia cells in the bone marrow lead to abnormal white blood cell production, which may be detected in the bloodstream, also called the peripheral circulation. Sometimes in leukemia, blood tests may show there are too many white blood cells and high numbers of early or immature blood cells in the circulation.

Other times, there may be high numbers of the blood-forming cells known as blasts out in the circulating blood. Leukemia cells may crowd out the normal blood-forming cells in the bone marrow, resulting in lower-than-normal levels of red blood cells, white blood cells, and platelets in the peripheral blood. Such shortages can be spotted in blood tests, and they can also cause symptoms.

Understanding Leukemia Types

The four main types of leukemia are:

  • Acute lymphoblastic leukemia (ALL)
  • Acute myelogenous leukemia (AML)
  • Chronic lymphocytic leukemia (CLL)
  • Chronic myelogenous leukemia (CML)

Each name, as you can see, reflects whether the cancer is considered an acute or chronic leukemia.

  • Acute leukemia usually progresses rapidly without treatment.
  • Chronic leukemia usually progresses more slowly. A chronic leukemia, however, may have the potential to ‘transform’ into a more aggressive, acute leukemia.

Acute leukemias, such as ALL and AML, develop from early, immature blasts. These blood-forming cells don’t stop dividing when normal blasts would, and growth and progression tend to be more rapid than in chronic leukemias.

Chronic leukemias like CLL and CML, on the other hand, arise from blood-forming cells that are more mature compared to blasts, though they are still abnormal. Blood tests in people with these leukemias may show few or no blast cells circulating. These cancers usually grow more slowly than the acute leukemias.

What Makes Leukemia Myelogenous or Lymphocytic?

In addition to whether it’s acute or chronic, it also matters whether a leukemia is myelogenous or lymphocytic because this, too, can help predict how the cancer will behave and how best to treat it.

To understand what these terms really mean, you need a brief overview of how your body normally makes new blood cells to replace the old ones that die or get worn out:

As different as they are, all adult red and white blood cells come from something like a ‘great-ancestor’ cell, called a hematopoietic stem cell, or HSC. You have many HSCs in your bone marrow and some in your blood, as well.

From each HSC, multiple ‘generations’ of blood-forming cells come forth in a series, through cell division, eventually giving rise to the familiar mature cell types found in human blood. Each generation is a step forward toward maturity, with the next generation emerging relatively quickly.

Cells that belong to different generations are given different names, such as progenitors or precursors, depending on how far back toward the HSC in the ‘family tree’ you go. As you move forward in time, away from the HSC, you can begin to tell which ‘family’ a blood-forming cell will give rise to.

The two most prominent families in the family tree are the lymphoid and myeloid families. Different terms are in use to refer to the same family; for instance, lymphoid and lymphocytic, and myeloid and myelogenous. 

  • Lymphocytic refers to the family that ultimately gives rise to adult lymphocytes, a group of white blood cells.
  • Myelogenous refers to the family that ultimately gives rise to red blood cells, non-lymphocytic white blood cells—including neutrophils, for instance—as well as cells that make your platelets, named megakaryocytes, which help blood to clot.

In leukemia, the cancer develops in a cell that is somewhere back in the 'family tree’ of new blood cells. Samples containing leukemia cells, including blood and biopsy samples, are analyzed in the laboratory to determine whether the cancerous cells are either myelogenous or lymphocytic. 

What Causes People To Get Leukemia?

In most cases, scientists don’t know precisely how leukemia begins. But for some leukemia types, risk factors have been identified. Risk factors are links that help scientists better understand the disease and its development. However, just because you have a risk factor does not mean you will necessarily develop that disease.

​Case in point: For AML, the following links have been found, but most people who get AML do not have these risk factors:

  • Smoking
  • Long-term exposures to high levels of benzene, a chemical found in cigarette smoke and used in certain industries
  • Past treatment with certain chemotherapy drugs
  • High doses of radiation
  • Certain genetic conditions present at birth
  • Having a close family member who got AM

High doses of radiation have also been linked to ALL and CML. Family history can also come into play in some instances, such as in CLL.

General Symptoms of Leukemia

Symptoms of leukemia are blatant in some cases and essentially absent in others, which we know is not comforting. They may come on gradually or suddenly. Sometimes initial signs and symptoms may be vague, such as flu-like symptoms and fatigue, or may include frequent infections. However, leukemia can also develop more visibly and acutely with more obvious warning signs. Symptoms to look out for include the following:

  • Fever
  • Recurrent infections
  • Abnormal bruising or bleeding
  • Fatigue
  • Weakness
  • Intolerance to physical exercise
  • Abdominal pain or fullness
  • Unintentional weight loss
  • Enlargement of the lymph nodes spleen and/or liver
  • Bone pain

The most common types of leukemia can produce symptoms such as bone and joint pain, fever, night sweats, fatigue, weakness, pale skin, easy bleeding or bruising, weight loss, and others, including swollen lymph nodes, spleen, and liver.

Symptoms of leukemia such as feeling excessively tired and weak, when from an inadequate supply of red blood cells, or anemia, may also be reflective of how much of the healthy bone marrow has been taken over by leukemia cells.

Symptoms of Specific Leukemia Types

Sometimes, a particular type or subset of leukemia may have a characteristic symptom or set of symptoms that is not as common in other types of leukemia.

For instance, acute promyelocytic leukemia, a subset of acute myelogenous leukemia, has some characteristic symptoms of both excessive bleeding and clotting, in addition to the usual, non-specific leukemia symptoms.

In acute lymphocytic leukemia, which mostly strikes children, the leukemia may enter the fluid around the brain and spinal cord, producing related symptoms such as headaches, blurred vision, nausea vomiting and seizures (in addition to usual non-specific symptoms). 

In chronic myelogenous leukemia, as many as 40 percent of patients may have no symptoms at all, and the diagnosis may follow from a routine check-up or a visit for another concern.

Leukemia Diagnosis

When symptoms, physical exam findings, medical history, and other clues suggest that leukemia is a possibility, a variety of different tests may be used to make an official diagnosis. Blood tests and bone marrow tests are generally needed to confirm the disease, and spinal taps may be done in some cases. Blood tests and bone marrow tests also help to identify AML, ALL, CML, and CLL subtypes. Samples from other sites may also be taken to help evaluate the leukemia and to help guide treatment.

Blood Tests

The complete blood count, or CBC, involves automated counting of blood cells of different types to determine whether your numbers fall in a normal or abnormal range. The CBC is often done along with a ‘differential’ count, which will provide numbers of each of the types of cells, such as neutrophils and lymphocytes, under the umbrella term 'white blood cell.'

The blood smear provides a closer look: It is done to evaluate blood cells microscopically, often after an automated CBC with differential indicates abnormal or immature cells are present. In a blood smear, the immature cells and abnormalities can be characterized to the extent possible by their microscopic appearance.

An initial diagnosis and evaluation also includes other blood tests, such as blood chemistries, to check for possible leukemia complications in other organs, for instance.

Bone Marrow Biopsy

A biopsy is a procedure in which a sample of cells is removed from the body for further study. A bone marrow biopsy usually begins with bone marrow aspiration, in which a small amount of fluid from the bone marrow is pulled into a syringe. Then, for the biopsy itself, a large needle is usually pressed with a twisting motion into bone (typically the hipbone) to obtain a small, cylindrical sample of marrow. Biopsy specimens are then examined by a pathologist and undergo further laboratory testing. Depending on the type of leukemia suspected, biopsies at other sites, such as the lymph nodes, may also be involved.

Lumbar Puncture/Spinal Tap

A lumbar puncture or spinal tap may be performed to diagnose leukemia. Under a local anesthetic, a needle inserted in an area of the backbone to access the fluid that surrounds and bathes the spine; a sample of the fluid is drawn out, along with any leukemia cells that may be present. A pathologist then analyzes this fluid.

Genetic Testing of Cancerous Cells

Genetic tests are often done on the abnormal cells as part of the diagnosis and evaluation of the leukemia. Cytogenic analysis refers to tests that examine changes in the chromosomes of the leukemia cells. Certain mutations and genetic rearrangements also help doctors predict how a malignancy might behave.

Scans and Imaging

Sometimes imaging scans play a role in helping doctors to locate cells in a particular part of the body for biopsy, or to determine if lymph nodes or other organs are enlarged.

Diagnosis of Different Leukemia Types

AML is diagnosed by bone marrow biopsy and laboratory analysis of the bone marrow cells. AML can sometimes spread to the fluid that surrounds the brain and spinal cord, so doctors may perform a lumbar puncture or spinal tap to have the fluid analyzed as well. Tests are also used to reveal the genetic profile of the AML, including chromosomal characteristics and specific genes and genetic changes.

CLL is diagnosed many times in people who lack symptoms. CLL might be considered as a possible diagnosis when an adult has a high absolute lymphocyte count, or elevation due to extra lymphocytes. High lymphocyte counts can also occur with other, non-cancerous conditions like infectious mononucleosis and pertussis, however; they also occur in certain other blood cancers.

In some cases of CLL, blood tests may be enough for the diagnosis, but testing the bone marrow is helpful to tell how advanced it is, and bone marrow tests are therefore often done before treatment. In some cases of CLL, part of a chromosome may be missing, which can affect the outlook, so genetic testing of the abnormal cells is also important.

CML, like CLL, is often diagnosed before a person has any symptoms. CML might first be suspected by identifying its typical findings in the blood and then bone marrow. Most patients with CML have too many white blood cells with many immature cells in their blood. Sometimes CML patients have low numbers of red blood cells or blood platelets. These findings may point to leukemia, but the diagnosis usually requires another blood test or a test of the bone marrow for confirmation.

In people with CML, the bone marrow is often ‘hypercellular,’ meaning it has more blood-forming cells than expected because it is full of leukemia cells. Some form of genetic testing of the abnormal cells is done to look for the Philadelphia chromosome and/or the BCR-ABL gene.

ALL is not usually diagnosed without examining the bone marrow. The majority of people with ALL have too many immature white blood cells in their blood, and not enough red cells or platelets. Many of the white blood cells will be lymphoblasts or blasts. These lymphoblasts are immature lymphocytes that do not function normally. Like AML, since ALL can spread to the area around the brain and spinal cord, the fluid that bathes these organs may be sampled via a lumbar puncture or spinal tap. As with other types of leukemia, special tests reveal characteristics of the abnormal cells to help determine the diagnosis and leukemia subtypes. For instance, one sample stain turns parts of the cells black if they are AML cells but not if they are ALL cells.

Chromosome testing also has a role in AML because, like CML, some people with ALL have a rearrangement in their chromosomes that leads to the Philadelphia chromosome. About 25 percent of adults with ALL have this abnormality in their leukemia cells.

Below are estimates for the number of new diagnoses of each type of leukemia in the United States each year:

  • 19,950 new cases of AML
  • 18,960 new cases of CLL
  • 8,220 new cases of CML
  • 6,590 new cases of ALL

When to See Your Doctor

You should make an appointment with your doctor if you have any persisting signs or symptoms that worry you. Leukemia symptoms can be vague and not specific. In some cases, leukemia is discovered during blood tests that are done for some other reason.

Since many of the symptoms of leukemia are also symptoms of much more common (and, in some cases, less concerning) illnesses, it's important not to panic. Working with your doctor can help put your physical findings or symptoms into context, allowing for careful consideration of the most appropriate next steps.

A Word From Verywell

A leukemia diagnosis can set your world upside-down. Whether it is you, a loved one, or perhaps your own child, leukemia is a diagnosis that nobody is ready for. Know that it is completely normal feel overwhelmed.

Education is the first step, and it will help you to take charge of your own cancer journey. In almost every case, there is also a healing process that also needs to take place—one that doesn’t come from an IV bag, pill, or transfusion.

Make use of supportive communities and resources. Learn from people who have walked in your shoes. Know that you are never alone, even if sometimes it feels like you are. And, always ask questions.

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