Cytogenic Studies for Leukemia Diagnosis
Leukemia is a blood cancer that affects white blood cells, which are responsible for fighting off infection in the body. When a person develops leukemia, these white blood cells, which are in the bone marrow, grow abnormally and crowd out healthy cells, interfering with the blood cells' work.
Diagnosing leukemia in its earliest stages can improve a patient’s prognosis, so it is important to be tested as soon as possible if leukemia is suspected. In this age of precision medicine, advancements in molecular cytogenetics have enabled doctors to determine the best treatment for the patient. "We are now on the forefront of medicine, when some of these cytogenetic findings make patients eligible for clinical trials that Yale Medicine is offering,” says Yale Medicine pathologist Alexa Siddon, MD.
What are the main types of leukemia?
There are multiple types of leukemia, which include:
- Acute lymphocytic leukemia
- Acute myeloid leukemia
- Chronic lymphocytic leukemia
- Chronic myeloid leukemia
Adults can get any type, but children tend to get acute leukemia. “Acute leukemia is made of blasts, immature cells, while chronic leukemia is made of more mature cells,” Dr. Siddon says. “Chronic leukemias tend to proliferate slower than acute leukemias, just because the blasts multiply very quickly. People with acute leukemia will become symptomatic more rapidly, in general.”
Leukemia that affects lymphoid cells, which would develop into lymphocytes (a form of white blood cell), is called lymphoid, lymphoblastic or lymphocytic leukemia.
Leukemia that affects myeloid cells, which would normally develop into red blood cells, platelets or granulocytes (a specific type of white blood cell), is called myeloid leukemia. Myeloid leukemia may also be called myelogenous or myeloblastic leukemia.
The prognosis depends on the type of leukemia and other risk factors, such as family and personal medical history.
What are the symptoms of leukemia?
According to Mina L. Xu, MD, a pathologist at Yale Medicine, symptoms of leukemia could include “night sweats, excessive fatigue, or others that are more flu-like.”
Leukemia is suspected if a person describes such initial symptoms to their physician as swollen lymph nodes, fever, chills, weakness, enlarged liver or spleen, weight loss, bone pain or tenderness. The doctor is likely to order additional tests to rule out other illnesses and pinpoint what's going on.
“Initial symptoms can be subtle,” Dr. Xu says, “unlike solid tumors, leukemia rarely presents with an actual mass.”
The challenge with diagnosing leukemia is that its vague symptoms can be easily confused with symptoms of the common cold or flu. The symptoms can also be nonspecific, such as general fatigue.
What are the risk factors for leukemia?
People who were exposed to specific chemotherapy agents for treatment of previous cancers may be at risk for developing certain forms of leukemia. “Also, there are some inherited risk factors,” Dr. Siddon says. “For example, chronic lymphocytic leukemia can run in families.”
Is there a test for leukemia?
Leukemia can be detected with routine tests, such as those included in an annual physical, before any symptoms even begin. If there is cause for concern, the doctor will probably order more evaluations, which could include:
- A physical exam, looking for signs of leukemia, such as swollen lymph node, anemia-related pale skin and enlarged spleen or liver.
- Blood tests. “This would include a CBC, or complete blood count, with cell differential to measure the amount of white blood cells and platelets in the blood,” says Mina L. Xu, MD, assistant professor of Pathology and associate director of Hematopathology at Yale Medicine.
- Bone marrow tests. A bone marrow sample may be taken from the hipbone and studied by pathologists to determine whether leukemia cells are present.
Pathologists who specialize in leukemia and lymphoma frequently examine “lymph nodes, blood and bone marrow – all key tissues where the key malignancy could be,” Dr. Xu says.
How is leukemia diagnosed?
If the blood test is suspicious for leukemia, a patient will typically work with a hematologist, who specializes in blood diseases. The hematologist will take a sample of bone marrow from the hipbone – a bone marrow biopsy and aspiration – that contains liquid and solid tissue parts.
A multidisciplinary team then performs a series of tests, in different labs, to determine the type of cancer and the best course of treatment, says Dr. Xu.
Flow cytometry. At Yale Medicine, some of the liquid parts of the tissue sample go to the Clinical Flow Cytometry Laboratory. "Flow cytometry is a very sensitive technology that uses a laser beam to identify the very specific types of cells found in a sample," Dr. Siddon says. "We can often diagnose the particular type of leukemia using flow cytometry because the technology allows us to differentiate between lymphoid or myeloblastic leukemia, which is important because they are treated with different chemotherapy regimens."
Flow cytometry can be performed on bone marrow or using blood – the latter is relatively noninvasive, says Dr. Siddon, because it uses blood drawn from the arm.
Biopsy analysis. The solid biopsy tissue sample, as well as a smear of tumor cells, goes to the pathology lab, where Dr. Xu and her colleagues examine the leukemia under the microscope and manually count the leukemia cells. This provides additional information about how the cancer arose, which helps determine prognosis. They may also reveal additional disease.
Molecular/Genetic testing. This also uses some of the liquid tumor to evaluate cytogenetics (the chromosomes within the cell) to look for chromosomal variations or abnormalities in the cells. "There are some specific cytogenetic abnormalities that are very specific to leukemia, and the presence or absence of these abnormalities can help us decide if a patient should have a particular chemotherapy regimen or possibly a bone marrow transplant," Dr. Siddon says.
In the end, all of this information is pooled together along with genetic data. Then, the pathologist and oncologists discuss the type of leukemia, the prognosis and the best treatment options for the patient.
How is Yale Medicine's approach to diagnosing leukemia unique?
“Prognosis for some types of leukemia, such as acute promyelocytic leukemia (APL), used to be quite poor,” Dr. Xu says. “There were no drugs specifically targeting mutations. But now, at Yale Medicine, we can get the particular mutation of the cell confirmed by our cytogenetics lab within 24 hours. A patient can get treated right away, and the prognosis is now considered fairly good.”
Dr. Xu says the short turnaround time to diagnosis can be critical for these patients. “Diagnosing leukemia is complex, because there are so many layers of testing that need to be incorporated,” she says. “Yet I find it reassuring that we have a lot of checks and balances in the diagnostic process.”
In this age of precision medicine, advancements in molecular cytogenetics have enabled doctors to determine the best treatment for the patient. "We are now on the forefront of medicine, when some of these cytogenetic findings make patients eligible for clinical trials that Yale Medicine is offering,” Dr. Siddon says.