– Characteristics of leukemia diagnosis and screening
– Diagnosis of acute leukemia: the myelogram
– Results of the myelogram
– Diagnosis of chronic leukemia: immunophenotyping of cells
– Results of immunophenotyping of cells
– Other diagnostic tests and screening
The diagnosis of leukemia, and related screening, is not always based on the manifestation of symptoms, as the chronic form of the disease may progress without the patient’s knowledge.
Particularities of leukemia diagnosis and screening
Leukemia can be suspected following the appearance of a set of suggestive symptoms or by a simple blood test. Nevertheless, for the two main types of leukemia, it is possible to carry out tests to establish a diagnosis:
– The diagnosis of acute leukemia can only be made after a precise examination under the microscope: the myelogram.
– For the diagnosis of chronic leukemia, the blood test may already reveal an increase in immature lymphocytes. In this case, we proceed to:
◦ immunophenotyping of the cells that will allow determining with more precision the lymphocytes involved and their morphology ;
◦ and, eventually, a lymph node biopsy may be considered under local anesthesia.
Inasmuch as the causes of blood cancers remain unknown, no preventive measures can be taken. According to statistics, these cancers remain relatively rare in adults. Therefore, it is impossible to set up a systematic screening for leukemia.
Diagnosis of acute leukemia: the myelogram
The myelogram is a crucial examination to determine whether or not a patient has acute leukemia. In concrete terms, it consists of analyzing the cells in the bone marrow using a microscope:
– A hematologist takes a sample of bone marrow from the breastbone or the iliac bone (side bone of the pelvis) under local anesthesia.
– The surgeon uses a hollow needle to aspirate a small amount of marrow (puncture).
– The procedure takes only a few seconds, but it is painful, so painkillers are prescribed simultaneously.
Results of the myelogram
The observation of the cells taken during the myelogram allows confirmation of the possible presence of acute leukemia. The analysis is positive if the onco-hematologist finds:
– more than 20% immature cells;
– and an insufficient number of neutrophilic white blood cells (found in 30% of cases);
– and an insufficient number of blood platelets (found in 80% of cases);
– and an insufficient number of red blood cells (in 90% of cases).
In addition, morphological analysis of the cells makes it possible to classify acute leukemia accurately and determine :
– whether it is acute myeloblastic leukemia (especially if the rate of medullary blasts – malignant cells – is greater than 20%) and which of the three existing subtypes it is;
– whether it is acute lymphoblastic leukemia (especially if the marrow blast rate is greater than 25%) and which of the eight existing subtypes it is;
– treatment of leukemia.
Because of the difficulty in identifying this disease, the diagnosis must be impeccable and precise.
Diagnosis of chronic leukemia: cell immunophenotyping
Immunophenotyping of cells is a necessary test that, together with the patient’s clinical examination, helps to determine whether or not the patient has chronic leukemia. In particular, this method will help determine the stage of leukemia detected. This is essential to set up the most appropriate treatment.
At the same time, it is usual to complete the immunophenotyping with the following examinations
– a myelogram to check that the marrow contains many immature cells.
– a study of the karyotype (chromosomes) of the cells, looking for the Philadelphia chromosome (24) in particular, to determine whether the patient has chronic myeloid leukemia.
Note: Fluorescence in situ hybridization (FISH) is used, in which dyes are attached to specific parts of certain chromosomes, detecting abnormalities.
Results of immunophenotyping of cells
Through immunophenotyping of the cells and, in parallel, the study of the karyotype, it is possible to obtain fairly precise results concerning the stage and phase of chronic leukemia.
The 3 possible stages
To interpret the results of the immunophenotyping, the Binet classification is used:
– It comprises 3 levels (A, B, and C).
– It focuses on:
◦ the tissues affected by leukemia (lymph nodes, spleen, and liver);
◦ the ancillary symptoms (anemia, i.e., lack of red blood cells, and thrombocytopenia, i.e., lack of platelets).
We then get the following description of the 3 levels:
– If the leukemia is in stage A, it means that:
◦ only increased lymphocyte count was found;
◦ no symptoms were detected;
◦ as a precautionary measure, monitoring is instituted every 6 to 12 months.
– If the leukemia is in stage B, this means that:
◦ splenomegaly (increased spleen volume) is found;
◦ and adenopathy (enlarged lymph nodes) involving at least three areas of the body (neck, armpit, and groin in general) is also detected;
◦ chronic lymphocytic leukemia is suspected.
– If the leukemia is in stage C, it means that:
◦ the increase in lymphocytes is accompanied by a decrease in red blood cells and platelets;
◦ the prognosis is poor.
Results following karyotype study
If the karyotype study reveals the presence of chronic myeloid leukemia, it will be specified whether the disease is:
– in the chronic phase, which is stabilized and asymptomatic because the healthy white blood cells and platelets retain their function ;
– in accelerated phase, which means that up to 30% of the cells are abnormal and affect the other blood cells (life expectancy is then 6 to 9 months in the absence of treatment);
– in a blast crisis, more than 30% of the blood cells are abnormal, and bone and lymph node tumors can be found (life expectancy is 3 to 6 months).
Other diagnostic and screening tests
More rarely, medical imaging tests may be used to detect leukemia:
– A chest x-ray or 3-D CT scan can show whether the lymph nodes or thymus are swollen.
– An MRI (magnetic resonance imaging) can look at the brain and spinal cord to see if leukemia has spread to the brain.
– An ultrasound can be used to check whether internal organs (kidneys, liver, spleen, etc.) are affected by leukemia.
Under local anesthesia, a lumbar puncture can also be performed under local anesthesia to remove cerebrospinal fluid (the fluid surrounding the spinal cord) and check for cancer cells.