Understanding Leukemia

Common Types of Leukemia

Leukemia types are categorized based on the affected white blood cells. It can originate in lymphoid cells or myeloid cells. Lymphoid leukemia affects lymphoid cells and is referred to as lymphocytic or lymphoblastic leukemia, while myeloid leukemia affects myeloid cells and is called myelogenous or myeloblastic leukemia.

There are four common types of leukemia:

• Acute lymphocytic (lymphoblastic) leukemia (ALL): ALL targets lymphoid cells and grows quickly. It develops in the bone marrow, where blood cells are made. Acute lymphoblastic leukemia is the most common type in young children, although it can also affect adults.
• Acute myeloid (myelocytic) leukemia (AML): AML impacts myeloid cells and grows quickly. It most commonly occurs in adults, but can also develop in children.
• Chronic lymphocytic leukemia (CLL): CLL affects lymphoid cells and usually grows slowly. It is most often diagnosed in adults and accounts for about one-third of all leukemias.
• Chronic myeloid (myelogenous) leukemia (CML): CML involves myeloid cells and typically grows slowly at first. It mainly affects adults and accounts for about 15% of leukemias.

Diagnosing Leukemia

Several tests and procedures are used to diagnose leukemia, including:

• Physical examination: The doctor will check for swollen lymph nodes in areas such as the neck, underarms, and groin, as well as for an enlarged spleen or liver.
• Blood tests: Various blood tests can help determine if symptoms are caused by leukemia or other conditions. 
• A complete blood count (CBC) measures the levels of red blood cells, white blood cells, and platelets.
• Flow cytometry and peripheral blood smear identify markers that indicate the presence of leukemia cells or a specific type of leukemia.
• Biomarker testing to identify any genetic changes in the cancer cells that can be treated with a targeted therapy or immunotherapy
• Lymph node biopsy: The doctor may recommend removing an entire lymph node (excisional biopsy) or part of a lymph node (incisional biopsy) for laboratory testing.
• Bone marrow aspiration and biopsy: Because leukemia cells can grow in the bone marrow, these tests are run to see if cancer cells are present. They may be repeated later to see how well the leukemia treatment is working. 
• Imaging: A CT scan can identify affected lymph nodes, and a PET scan can detect cancer cells developing in a specific area of the body, even if they aren’t yet visible on other images.

Other Tests for Diagnosing and Staging Leukemia 

The specific tests your doctor orders depend on your symptoms and the type of leukemia. Additional tests may include:

• Cytogenetics: This test examines the chromosomes of cells from blood, bone marrow, or lymph node samples. Identifying any abnormal chromosomes can help determine the specific type of leukemia you have. For example, people with CML have an abnormal chromosome called the Philadelphia chromosome.
• Spinal tap or lumbar puncture: Some leukemia types, such as ALL and AML, can spread to the brain and spinal cord. To determine the extent of these types of leukemia, blood cancer doctors might remove a sample of cerebrospinal fluid (CSF) for testing. This involves inserting a small needle between the bones around the spinal cord to remove CSF.
• Chest x-ray: An x-ray can show swollen lymph nodes or other signs of disease in the chest.