Diagnosing Leukemia in Children

Childhood leukemia, a type of blood cancer that causes a higher-than-normal production of white blood cells in the body, accounts for nearly one in three cancers in children. At Hassenfeld Children’s Hospital at NYU Langone, our doctors diagnose and treat three of the main types of childhood leukemia, all of which begin in the bone marrow, the tissue at the center of each bone in the body.

Bone marrow produces immature cells, called stem cells, that develop into specialized types of blood cells. These include platelets, which aid in blood clotting; red blood cells, which carry oxygen throughout the body; and white blood cells, which help the body fight infection. In childhood leukemia, the bone marrow produces abnormal white blood cells that crowd out all of the other healthy blood cells, preventing them from doing their jobs.

Because there are several types of leukemia, an accurate diagnosis is essential to determining the right treatment.

Symptoms of Childhood Leukemia

Although leukemia may cause no symptoms, some children exhibit signs of the condition that may be noticeable to their parents and doctors. These can include a tendency to bruise or bleed easily, especially from the gums or nose; persistent, low-grade fevers; unusually pale skin; swollen lymph nodes, particularly in the throat, armpits, or groin; and a feeling of fullness under the ribs, which can be caused by an enlarged spleen and bone pain. 

Many of these symptoms and signs also indicate other health conditions. For this reason, our doctors take a medical history, perform a physical exam, and order blood tests. Blood tests can reveal very low levels of normal white and red blood cells and platelets with or without the presence of an excessive amount of abnormal white blood cells—a sign of leukemia.

Diagnostic Tests

Our pediatric oncologists perform certain diagnostic tests in order to identify the presence of leukemia. The results of these tests help doctors to determine the type of leukemia and the risk group, which refers to the prognosis, or the severity of the leukemia.

Blood Tests

During an initial exam, our specialists take a sample of your child’s blood to check white blood cell levels and to determine the type of white blood cells circulating in the blood. They also check if there are low numbers of normal while blood cells, red blood cells, and platelets circulating in the blood.

Bone Marrow Aspiration and Biopsy

Because leukemia starts in the bone marrow, bone marrow aspiration and biopsy is often essential to helping doctors diagnose the type of leukemia. During this procedure, performed under sedation and monitored by a pediatric anesthesiologist, your doctor uses a small needle to remove a sample of bone marrow fluid, most commonly from the pelvic bone in the lower back.

A hematopathologist, a doctor who specializes in analyzing cells to diagnose leukemia, then reviews the collected cells under a microscope in a laboratory. The cells are also examined using an instrument called a flow cytometer, which detects certain proteins on the surface of cells that indicate the type of blood cell and whether it is an abnormal, or leukemic, blood cell.

Lumbar Puncture

In a lumbar puncture, performed under sedation, a small needle is inserted into the lower back to withdraw spinal fluid for laboratory testing by a pathologist. This test is used to determine if cancer cells are present in the central nervous system, which can influence the type of leukemia treatment your child receives.

Chromosome Analysis

Chromosomes are the components of cells that carry a person’s genetic information. Also called karyotyping, a chromosomal analysis of cells collected during bone marrow aspiration can identify genetic abnormalities in the leukemia cells that may help doctors to determine the type of leukemia.

For example, in some childhood leukemias, a switching, or translocation, of chromosomes occurs, which provides a signal for the leukemia to grow. Knowing about the presence of this chromosomal translocation helps your child’s doctor to diagnose and treat this type of leukemia.

At Hassenfeld Children’s Hospital, your child’s doctor orders a newer type of test called fluorescence in situ hybridization (FISH), and gene sequencing, which can identify malfunctioning genes by mapping them, to detect chromosomal changes that conventional karyotyping doesn’t recognize.