After chronic myelogenous leukemia has been diagnosed, tests are done to find out if the cancer has spread.

Staging is the process used to find out how far the cancer has spread. There is no standard staging system for chronic myelogenous leukemia (CML). Instead, the disease is classified by phase: chronic phase, accelerated phase, or blastic phase. It is important to know the phase in order to plan treatment. The following tests and procedures may be used to find out the phase:

• Cytogenetic analysis: A test in which cells in a sample of blood or bone marrow are viewed under a microscope to look for certain changes in the chromosomes, such as the Philadelphia chromosome.
• Bone marrow aspiration and biopsy: The removal of bone marrow, blood, and a small piece of bone by inserting a needle into the hipbone or breastbone. A pathologist views the bone marrow, blood, and bone under a microscope to look for abnormal cells.

Chronic myelogenous leukemia has 3 phases.

As the amount of blast cells increases in the blood and bone marrow, there is less room for healthy white blood cells, red blood cells, and platelets. This may result in infections, anemia, and easy bleeding, as well as bone pain and pain or a feeling of fullness below the ribs on the left side. The number of blast cells in the blood and bone marrow and the severity of symptoms determine the phase of the disease.

Chronic phase

In chronic phase CML, fewer than 10% of the cells in the blood and bone marrow are blast cells.

Accelerated phase

In accelerated phase CML, 10% to 19% of the cells in the blood and bone marrow are blast cells.

Blastic phase

In blastic phase CML, 20% or more of the cells in the blood or bone marrow are blast cells. When tiredness, fever, and an enlarged spleen occur during the blastic phase, it is called blast crisis.