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Philadelphia chromosome positive

(FIH-luh-DEL-fee-uh KROH-muh-some PAH-zih-tiv)
Describes cancer cells that have an abnormal chromosome called the Philadelphia (Ph) chromosome. The Ph chromosome is made when part of the ABL1 gene on chromosome 9 breaks off and attaches to the BCRgene on chromosome 22 to form the BCR::ABL1 fusion gene. The protein made by the BCR::ABL1 fusion gene can cause immature white blood cells to grow uncontrollably and build up in the bone marrow and blood. The Ph chromosome is found in the bone marrow cells of almost all people with chronic myelogenous leukemia and some people with acute lymphocytic leukemia or acute myelogenous leukemia. Knowing whether a cancer is Ph chromosome positive may help plan treatment.
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