NCCN Guidelines for Patients® | Chronic Myelogenous Leukemia - page 17

17
NCCN Guidelines for Patients
®
: Chronic Myelogenous Leukemia
Version 1.2014
Definitions:
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See Part 1 on page
X for definitions of
other lung parts.
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Blood st m cell:
A
immature cell that f rms all
other types of blood cells
Fusion gene:
Gene made
by joining (fusing) parts of
two separate genes
Gene:
Set of instructions
in cells for making and
controlling cells
Kidneys:
Pair of organs
that remove waste from the
body through urine
Liver:
Organ that removes
waste from the blood
Lymphoid:
Referring to
a type of white blood cell
called a lymphocyte
Myeloid:
Referring to a
type of white blood cell
called a granulocyte
Philadelphia
chromosome:
A short
chromosome 22, formed
when parts of chromosome
9 and 22 switch with each
other
2.3 Lab tests
blood and the number of basophils is very low. But in the advanced phases of
CML, the number of basophils is increased and many blast cells are found in the
bone marrow or peripheral blood.
Bone marrow cytogenetics
Cytogenetics is the study of chromosomes—long strands of bundles of coded
instructions for making and controlling cells. Bone marrow cytogenetics, also
called conventional cytogenetics, involves examining the bone marrow sample
with a microscope to look for changes in the cells’ chromosomes. This type of
test is used to detect the Philadelphia chromosome and measure the number of
cells that have it. The pathologist will use a microscope to examine a “map” of the
chromosomes, called a karyotype. The pathologist will assess the size, shape,
number, arrangement, and structure of the chromosomes on the karyotype to look
for any abnormal changes.
Cytogenetic testing can also be performed on cells from the peripheral blood, but
bone marrow is preferred. This is because the yield from peripheral blood is very
poor. Analysis of peripheral blood may be used if a bone marrow sample cannot
be collected (see below). Bone marrow cytogenetics is used to diagnose CML and
determine the disease phase (discussed in Part 3). It is also used to monitor how
well treatment is working—called a treatment response.
Fluorescence in situ hybridization
FISH (
f
luorescence
i
n
s
itu
h
ybridization) is another test used to detect the
Philadelphia chromosome and the
BCR-ABL
fusion gene. This test may be used
on a peripheral blood sample if a bone marrow sample can’t be collected. FISH
uses color “probes” to find the
BCR
gene and the
ABL
gene in chromosomes. The
BCR-ABL
fusion gene, located on the Philadelphia chromosome, is shown by the
overlapping colors of the two probes. FISH analysis of peripheral blood may be
used to diagnose CML when bone marrow cytogenetics isn’t possible. But, FISH
is not recommended for monitoring the response to treatment.
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