NCCN Guidelines for Patients
Acute Lymphoblastic Leukemia, Version 1.2017
Testing for ALL
Many types of chromosome changes can happen
in ALL. The leukemia cells may have an abnormal
number of chromosomes—too many or too few. The
leukemia cells may also have more than one type of
Sometimes parts of chromosomes break off and
switch with each other. This is called a translocation.
The Philadelphia chromosome is a key example of
a translocation that happens in some people with
ALL. The Philadelphia chromosome is caused by a
translocation between parts of chromosomes 9 and
See Figure 6.
This translocation also forms the abnormal
fusion gene on the Philadelphia
chromosome. A fusion gene is a new gene that is
formed when parts of two separate genes are joined
ybridization) is a very
sensitive lab test that can detect certain abnormal
changes in a cell’s genes or chromosomes. It can
detect most abnormal changes that can be seen
with a microscope. It can also detect some changes
that are too small to be seen with basic cytogenetic
chromosome is formed by a
translocation between parts
of chromosomes 9 and 22.
It contains the abnormal
This is a key chromosome
change that affects which
treatments are best for you.
Chromosomes break Changed chromosomes
Illustration Copyright © 2017 National Comprehensive Cancer Network