Diagnosis of Acute Myeloid Leukemia

Executive Summary

Several diagnostic tests help diagnose acute myeloid leukemia. The major procedures to diagnose acute myeloid leukemia include checking a patient’s medical history, complete blood cell count, physical examination, and bone marrow aspiration. The common diagnostic tests for acute myeloid leukemia include blood tests, bone marrow aspiration and biopsy, and molecular and genetic testing to identify specific genes, proteins, and other factors involved in leukemia (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

Several tests are necessary to diagnose cancer. They also do tests to see if cancer has metastasized or spread to another part of the body from where it began. For instance, imaging tests can determine 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 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. However, the doctor may suggest other tests if a biopsy cannot help diagnose the disease.

The doctor may consider the 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, these tests can also help 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 leukemia 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 “anesthesia” beforehand to numb the area. Anaesthesia is a medication that blocks the awareness of pain.

Molecular and genetic testing

Your doctor may also recommend running laboratory tests to identify specific genes, proteins, and other factors involved in leukemia. Examining the genes in the leukemia cells is essential because the cause of AML can be due to the buildup of mistakes (mutations) in the cell’s genes. In addition to it, identifying these mutations helps diagnose the specific subtype of AML and decide treatment options. Additionally, the results of those tests can help us monitor how well the treatment is working. Mentioned below are the more common molecular or genetic tests used for AML ^​3​.

Cytochemical and immunohistochemical tests

Cytochemical and immunohistochemical tests are laboratory tests that help to determine the exact subtype of AML. Furthermore, in cytochemical tests, a specific dye that stains the different types of leukemia cells differently based on the chemicals in the cells. For AML, immunohistochemical tests and a test known as flow cytometry helps to find markers on the surface of the leukemia cells. The different subtypes of leukemia have different and unique combinations of cell surface markers.

Cytogenetics

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 leukemia 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. The cause of some leukemia subtypes may be 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 also one of the ways to detect chromosome changes in cancer cells. It also helps diagnose and determine the subtype of leukemia. This is done on tissue removed in aspiration or biopsy.

The molecular genetics of leukemia cells can also determine if a person needs more or less chemotherapy or bone marrow/stem cell transplantation. This type of testing looks for minute genetic mutations, called sub-microscopic mutations.

Imaging tests

These imaging tests may help to learn more about the cause of symptoms or help diagnose infections in patients having AML. However, they are not the regular tests to find out how widespread AML is. This is because the disease has usually spread throughout the bone marrow when it is first diagnosed.

CT scan

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 determines 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 specialty centre where pediatric radiologists can supervise it. These centres are aware of the potential risks of radiation exposure from a CT scan.

MRI

An MRI uses magnetic fields, not x-rays, to produce detailed body images. MRI can also 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

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 help find a myeloid sarcoma and determine how well treatment is working against the sarcoma.

A lumbar puncture

It is also known as a spinal tap. In this procedure, 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 anesthetic before the procedure or other medications to calm or relax (sedation). The CSF undergoes an examination under the microscope to look for AML cells. Patients with AML do not need to have a lumbar puncture.

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