What is Acute Lymphocytic Leukemia (ALL)?

Acute lymphocytic leukemia (ALL) is a cancer that affects the bone marrow and the blood. ALL may also be referred to as acute lymphoblastic leukemia or acute lymphoid leukemia. All these terms refer to a blood cancer that begins from lymphoid cells, which can become B cells, T cells, and natural killer cells. “Acute” means that this type of cancer is fast growing and can progress quickly if not treated. However, many types of ALL tend to respond well to treatment.1,2

The cells that make up the blood, including white blood cells, red blood cells, and platelets, are made in the bone marrow. When a lymphoid cell becomes cancerous, it rapidly multiplies and can crowd out normal, healthy cells. ALL begins in the bone marrow, but it can quickly spread to other areas of the body, including the central nervous system and the lymph nodes.1,2

How does acute lymphocytic leukemia develop?

Blood is made up of several different cells, each with its own purpose. Red blood cells carry oxygen to the tissues, platelets help stop bleeding by creating clots, and white blood cells are the immune system’s primary defense and are critical for fighting infections. Each of these blood cells are created in the bone marrow, the spongy center portion of bones. The bone marrow contains blood stem cells, which are immature cells that can become different types of cells in the body. The stem cells differentiate into myeloid cells or lymphoid cells. Lymphoid cells can become cells such as B cells, T cells, and natural killer cells. ALL is a blood cancer that begins from lymphoid cells, and ALL can be divided into subtypes including B cell leukemias and T cell leukemias.2-4

A gene is a segment of DNA that is passed from parent to child. Genes are arranged into structures called chromosomes, and each person has 23 pairs of chromosomes.5 Each time any cell in the body divides, it makes a new copy of its DNA. Sometimes errors occur during this replication.1

These errors can cause the cell to develop abnormally and may lead to the development of cancer through the activation of oncogenes or the suppression of tumor suppressor genes. Oncogenes can cause the cells to replicate more, which can result in cancer. Tumor suppressor genes are normally a stop mechanism that cause damaged cells to die or slow cell growth. When tumor suppressor genes are turned off, cancer cells can replicate more easily.1

The Philadelphia chromosome

One of the most common translocations known in ALL in adults is called the Philadelphia chromosome. A translocation is a type of error that occurs during DNA replication, in which part of one chromosome is mistakenly switched with part of another chromosome. The Philadelphia chromosome occurs in approximately 1 in 4 cases of ALL in adults.1

The Philadelphia chromosome is named for the city it was discovered in, and its discovery, in the 1960’s, made it the first chromosomal abnormality conclusively linked to a type of cancer. If a person’s cancer has the Philadelphia chromosome, it is called Philadelphia chromosome-positive ALL, or PH+ ALL.6

The Philadelphia Chromosome

What are the different types of acute lymphocytic leukemia?

There are several different types of ALL, and determining the type is important for treatment recommendations. There are two main subtypes: B cell ALL and T cell ALL, named for the type of white blood cell they develop from. Most cases of ALL are B cell ALL.2

Additional categorizations of ALL include:

  • Acute B lymphoblastic leukemia
  • Early precursor B ALL (also known as early pre-B ALL or pro-B ALL)
  • Common ALL
  • Pre-B ALL
  • Mature B cell ALL (also known as Burkitt leukemia)
  • Philadelphia-positive ALL (Ph+ ALL)
  • Acute T-lymphoblastic leukemia
  • Natural killer cell leukemia1,2

Who gets acute lymphocytic leukemia?

ALL is more common in children than adults, although approximately 4 in every 10 cases occur in adults. The risk of ALL is greatest in children younger than 5 years of age. The risk declines after age 5 until approximately the mid-20’s. Another age group that has a greater likelihood of ALL are adults after age 50.1

ALL is slightly more common in males than females, and it is more common in whites than African Americans.1

What factors increase a person’s risk of developing acute lymphocytic leukemia?

Risk factors are characteristics that can increase someone’s chances of developing a disease, like ALL. Only a few risk factors for ALL are known, including:

  • Being exposed to high levels of radiation, including from previous radiation treatment for another cancer
  • Exposure to some chemicals, like benzene (found in gasoline, the rubber industry, the chemical industry, cigarette smoke, and some cleaning products)
  • Some viral infections, including human T cell lymphoma/leukemia virus-1 (HTLV-1) or Epstein-Barr virus (mononucleosis or “mono”)
  • Genetic disorders, like Down’s syndrome, Klinefelter syndrome, Fanconi anemia, Bloom syndrome, ataxia-telangiectasia, or neurofibromatosis
  • Being male (the risk is slightly higher in males than females)
  • Being white (ALL is more common in whites than African Americans)
  • Having an identical twin with ALL1

What are common symptoms of acute lymphocytic leukemia?

The crowding out of the healthy blood cells by ALL can cause complications such as:

  • Anemia, which is a lack of red blood cells and can cause fatigue
  • Neutropenia, which is a lack of neutrophils (a type of white blood cell) that puts a person at risk for infections
  • Thrombocytopenia, which is a lack of platelets and puts a person at risk for bleeding or bruising
  • Pancytopenia, which is a lack of all three: red blood cells, white blood cells, and platelets2

These complications can create symptoms of:

  • Frequent bruises, especially without a clear reason (like a fall or bump)
  • Fatigue, weakness, or tiredness
  • Repeated infections, or infections that don’t go away
  • Dizziness or feeling lightheaded
  • Fevers
  • Easily bleeding, such as from cuts, from the gums, or frequent nose bleeds
  • Shortness of breath
  • Achiness in the arms, legs, or hips
  • Weight loss with no apparent reason1,2

How does acute lymphocytic leukemia progress?

As an acute leukemia, ALL can progress very quickly. The type of damaged lymphoid cell that becomes cancerous is called a leukemic lymphoblast. These can rapidly multiply and can block the production of normal blood cells. The leukemic cells fill the blood and bone marrow and can progress to the lymph nodes, spleen, liver, central nervous system (the brain and spinal cord), and potentially the testicles in males.2,7 Because ALL can progress quickly, treatment is usually begun quickly after diagnosis is made.2

How is acute lymphocytic leukemia staged?

A standard staging system does not exist for ALL.6 ALL is generally classified by its subtype, which can help to guide treatment recommendations. B cell ALL and T cell ALL are the two main subtypes, named for the type of white blood cell they develop from. ALL may also be classified as untreated ALL, ALL in remission, relapsed ALL, which means the leukemia has returned after a period of remission, or refractory ALL, which means that the leukemia has not responded to treatment.1,6

What is the prognosis for acute lymphocytic leukemia?

While most cases of ALL happen in children, most of the deaths from ALL occur in adults with the disease. This may be due to differences in the cancer between children and adults, or it may be due to the fact that children’s bodies can often tolerate more aggressive treatment than adults.1

Over the past few decades, the survival rate for leukemia, including ALL, has been steadily increasing. (Survival rates are based on previous outcomes of people who survive a set amount of time after diagnosis. In cancer estimates, experts use the “five-year survival rate” as a marker. However, it is important to keep in mind that many people live beyond five years after diagnosis and the statistics are not necessarily predictive for any one individual.) Based on data from 2007-2013 (the most recent data available), the National Cancer Institute has determined the five-year survival rate for ALL overall is 68.2%, and the five-year survival rate for children and adolescents (younger than 15 years) with ALL is 92.3%.2,8

Written by: Emily Downward | Last reviewed: February 2018
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