Diagnosis of Acute Myeloid Leukemia

Executive Summary

Several diagnostic tests are conducted to determine acute myeloid leukemia. The main procedures to diagnose acute myeloid leukaemia are a patient’s medical history, complete blood cell count, physical examination, and bone marrow aspiration. The common diagnostic tests for acute myeloid leukaemia include blood tests, bone marrow aspiration and biopsy, and molecular and genetic testing to identify specific genes, proteins, and other factors involved in leukaemia (Cytochemical and immunohistochemical tests, Cytogenetics, Fluorescence-in-situ-hybridization (FISH)), molecular genetics, lumbar puncture and imaging tests (Computed tomography (CT or CAT) scan, Magnetic Resonance Imaging (MRI), and PET scan).

Diagnosis of Acute Myeloid Leukemia

Many tests are performed to find or diagnose cancer. They also do tests to see if cancer has spread to another part of the body from where it began. If this happens, it is called metastasis. For instance, imaging tests can represent if cancer has spread. Imaging tests show pictures of the body from the inside. Doctors can also do tests to learn which treatments would work best.

A biopsy is the sure short way for the doctor to know if an area of the body has cancer for most types of cancer. In a biopsy, the doctor takes a small tissue sample for testing in a laboratory. The doctor may suggest other tests if a biopsy cannot help diagnose.

The doctor may consider given factors when choosing a diagnostic test:

  • Your signs and symptoms
  • The age and general health status
  • The type of cancer suspected
  • The result of earlier medical tests

In addition to a physical examination, the below-mentioned tests may be used to diagnose AML ​1​

  • Blood tests – To diagnose AML, a doctor will do blood tests to count the number of white blood cells and see if they look abnormal under the microscope. Special tests called immunophenotyping or flow cytometry and cytochemistry are sometimes used to distinguish AML from other types of leukaemia and determine the exact subtype of AML ​2​.
  • Bone marrow aspiration and biopsy – These two procedures are similar and often done simultaneously to evaluate the bone marrow, which is the fatty, spongy tissue found inside larger bones. Bone marrow has both a liquid and a solid part. A bone marrow aspiration takes a sample of the fluid using a needle. A bone marrow biopsy removes a small quantity of solid tissue using a needle.

A pathologist then reviews the samples in a lab. Pelvic bone located by the hip is a common site for bone marrow aspiration and biopsy. Doctors generally give a medication called “anaesthesia” beforehand to numb the area. Anaesthesia is a medication that blocks the awareness of pain.

  • Molecular and genetic testing – Your doctor may recommend running laboratory tests to identify specific genes, proteins, and other factors involved in leukaemia. Examining the genes in the leukaemia cells is essential because AML can be caused by a buildup of mistakes (mutations) in the cell’s genes. Identifying these mutations helps diagnose the specific subtype of AML and decide treatment options. Additionally, the results of those tests can also be used to monitor how good treatment is working. Mentioned below are the more common molecular or genetic tests used for AML ​3​.
    • Cytochemical and immunohistochemical tests are laboratory tests used to determine the exact subtype of AML. In cytochemical tests, a specific dye is used that stains the different types of leukaemia cells differently based on the chemicals in the cells. For AML, immunohistochemical tests and a test known as flow cytometry are used to find markers on the surface of the leukaemia cells. The different subtypes of leukaemia have different and unique combinations of cell surface markers.
    • Cytogenetics is a way to look at a cell’s chromosomes through a microscope to analyze the number, shape, size, and arrangement of the chromosomes to find genetic changes in the leukaemia cells. Sometimes, a chromosome part breaks off and reattaches to another chromosome, known as translocation. Other times, part of a chromosome is missing, known as deletion. A chromosome can be made more than once, most often called trisomy. Some leukaemia subtypes are caused by chromosome translocations, deletions, or trisomies ​4​.

Knowing if specific translocations may help doctors determine the AML subtype and plan the best treatment. Fluorescence-in-situ-hybridization (FISH) is a way to detect chromosome changes in cancer cells and is being used often to help diagnose and determine the subtype of leukaemia. This test is done on tissue removed in aspiration or biopsy.

  • The molecular genetics of leukaemia cells can also be used to help find out if a person needs more or less chemotherapy or bone marrow/stem cell transplantation. This type of testing looks for tiny genetic mutations, called sub-microscopic mutations.
  • Imaging tests – The imaging tests listed below may be used to learn more about the cause of symptoms or help diagnose infections in patients having AML. They are not used regularly to find out how widespread the AML is because the disease has usually spread throughout the bone marrow when it is first diagnosed.
    • A CT scan takes pictures of the body from inside using x-rays taken from different angles. A computer then combines these pictures into a detailed, 3-dimensional image showing abnormalities or tumours. A CT scan can be used to determine the tumour’s size. Occasionally, a specific dye called a contrast medium is given before the scan to provide detail on the image. This dye can be delivered into a patient’s vein or provided as a pill or liquid to swallow. Whenever possible, it is best to do this test in a pediatric speciality centre where pediatric radiologists can supervise it. These centres are aware of the potential risks of radiation exposure from a CT scan.
    • An MRI uses magnetic fields, not x-rays, to produce detailed body images. MRI can also be used to determine the tumor’s size. A specific dye called a contrast medium is given before the scan to form a clearer picture. This dye can be delivered into a patient’s vein or given as a pill or liquid to swallow.
    • PET scan creates images of organs and tissues present inside the body. A small quantity of a radioactive substance is injected into the patient’s body which is taken up by cells using the most energy. The cancer cells which use energy actively take up the radioactive substance, and the scanner then spots this substance to produce images of the inside of the body. However, the radioactivity in the substance is significantly less harmful to patients. A scanner then detects this radioactive substance to produce images of the inside of the body. A PET scan may be used to find a myeloid sarcoma and determine how well treatment is working against the sarcoma.

A lumbar puncture, also known as a spinal tap, is a procedure in which a needle takes a sample of cerebrospinal fluid (CSF) to look for cancer cells or tumor markers. Tumor markers are materials found in greater than normal amounts in the urine, blood, or body tissues of people with specific kinds of cancer. Cerebrospinal fluid is the fluid that flows around the brain and the spinal cord. Patients are often given an anaesthetic to numb the lower back before the procedure or other medications to calm or relax their child (sedation). The CSF is then evaluated under the microscope to look for AML cells. Patients with AML do not need to have a lumbar puncture.

References

  1. 1.
    Arber DA, Erba HP. Diagnosis and Treatment of Patients With Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). American Journal of Clinical Pathology. Published online August 31, 2020:731-741. doi:10.1093/ajcp/aqaa107
  2. 2.
    Arber DA, Borowitz MJ, Cessna M, et al. Initial Diagnostic Workup of Acute Leukemia: Guideline From the College of American Pathologists and the American Society of Hematology. Archives of Pathology & Laboratory Medicine. Published online February 22, 2017:1342-1393. doi:10.5858/arpa.2016-0504-cp
  3. 3.
    Voso MT, Ferrara F, Galimberti S, Rambaldi A, Venditti A. Diagnostic Workup of Acute Myeloid Leukemia: What Is Really Necessary? An Italian Survey. Front Oncol. Published online February 17, 2022. doi:10.3389/fonc.2022.828072
  4. 4.
    Nguyen L, Zhang X, Roberts E, et al. Comparison of mutational profiles and clinical outcomes in patients with acute myeloid leukemia with mutated RUNX1 versus acute myeloid leukemia with myelodysplasia-related changes with mutated RUNX1. Leukemia & Lymphoma. Published online February 24, 2020:1395-1405. doi:10.1080/10428194.2020.1723016