NCCN Guidelines for Patients
Acute Lymphoblastic Leukemia, Version 1.2017
Testing for ALL
At the lab, a pathologist will look at the cells in a
blood or bone marrow sample with a microscope.
This test is simply called cell assessment. Doctors
may also refer to this test as a morphologic
assessment. Special dyes may be used to stain the
sample. This helps to show the differences between
parts of a single cell and between many cells.
The pathologist will look at the size, shape, type,
and other features of the cells in the blood or bone
marrow sample. This is to see if the cells look more
like normal, mature cells or more like abnormal,
immature cells. The number of very immature cells—
blast cells—in the sample is important.
Normally, there are no blast cells in the blood. And,
in a healthy person, blast cells make up no more
than 5% of cells in the bone marrow. This means
that no more than 5 out of every 100 cells in the
bone marrow are blast cells. In a person with ALL,
blast cells make up 25% or more of cells in the bone
marrow. This means that at least 25 out of every 100
cells are blast cells.
Flow cytometry is used to identify and count types
of cells in a sample. It can show if cells are normal
or abnormal. It can also tell the difference between
types of leukemia cells. This test is used to help
confirm ALL and find out the type of lymphocytes in
which it started. Flow cytometry is also used to check
ALL cells have a common pattern or “signature” of
proteins. The type and pattern of proteins differs
based on the type of maturity of the cell. The pattern
of surface proteins is called the immunophenotype.
Flow cytometry can identify the type of leukemia cells
present based on the pattern of surface proteins.
This is called immunophenotyping. A sample of bone
marrow is often used for immunophenotyping, but a
blood sample may also be used.
Flow cytometry involves first adding a marker—a
light-sensitive dye—to cells. The marker reacts with
surface proteins found only on certain types of cells.
The cells are then passed through a flow cytometry
machine. The machine identifies leukemia cells
based on the pattern of surface proteins. It can also
count the number of leukemia cells present. This is
helpful for checking treatment results.
Flow cytometry is sometimes used to measure the
amount of DNA in the leukemia cells. In such cases,
a marker that reacts with DNA is used. The amount
of DNA reflects the number of chromosomes in the
cells. This can help to show if the cells have too
many or too few chromosomes.
Cytogenetic testing uses a microscope to examine
the chromosomes inside cells. This type of test
is used to look for abnormal changes in the
chromosomes of the leukemia cells. It is often done
on a sample of bone marrow. It can also be done on
a sample of blood.
Certain chromosome changes in the leukemia cells
can affect treatment options and outlook. Thus, this
is a key test that is used to help plan treatment for
ALL. This test is given along with other initial tests
when ALL is first diagnosed. It may also be repeated
to check treatment results.
For this test, a pathologist will look at a “map” of
the chromosomes under a microscope. This map
is called a karyotype. It will show if there are any
abnormal changes in the size, shape, structure, or
number of chromosomes. This test can also be used
to count the number of leukemia cells.