General Information About Myelodysplastic/ Myeloproliferative Neoplasms

Myelodysplastic/myeloproliferative neoplasms are a group of diseases in which the bone marrow makes too many white blood cells.

Myelodysplastic/myeloproliferative neoplasms are diseases of the blood and bone marrow.

Normally, the bone marrow makes blood stem cells (immature cells) that become mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell. A lymphoid stem cell becomes a white blood cell. A myeloid stem cell becomes one of three types of mature blood cells:

• Red blood cells that carry oxygen and other substances to all tissues of the body.
• Granulocytes, which are white blood cells that help fight infection and disease.
• Platelets that form blood clots to stop bleeding.

Myelodysplastic/myeloproliferative neoplasms have features of both myelodysplastic syndromes and myeloproliferative neoplasms.

In myelodysplastic diseases, the blood stem cells do not mature into healthy red blood cells, white blood cells, or platelets. The immature blood cells, called blasts, do not work the way they should and die in the bone marrow or soon after they enter the blood. As a result, there are fewer healthy red blood cells, white blood cells, and platelets.

In myeloproliferative diseases, a greater than normal number of blood stem cells become one or more types of blood cells and the total number of blood cells slowly increases.

This summary is about neoplasms that have features of both myelodysplastic and myeloproliferative diseases. See the following PDQ summaries for more information about related diseases:

• Myelodysplastic Syndromes Treatment
• Chronic Myeloproliferative Neoplasms Treatment
• Chronic Myelogenous Leukemia Treatment

There are different types of myelodysplastic/myeloproliferative neoplasms.

The 3 main types of myelodysplastic/myeloproliferative neoplasms include the following:

• Chronic myelomonocytic leukemia (CMML).
• Juvenile myelomonocytic leukemia (JMML).
• Atypical chronic myelogenous leukemia (CML).

When a myelodysplastic/myeloproliferative neoplasm does not match any of these types, it is called myelodysplastic/myeloproliferative neoplasm, unclassifiable (MDS/MPN-UC).

Myelodysplastic/myeloproliferative neoplasms may progress to acute leukemia.

Tests that examine the blood and bone marrow are used to diagnose myelodysplastic/myeloproliferative neoplasms.

The following tests and procedures may be used:

• Physical exam and health history: An exam of the body to check general signs of health, including checking for signs of disease such as an enlarged spleen and liver. A history of the patient’s health habits and past illnesses and treatments will also be taken.
• Complete blood count (CBC) with differential: A procedure in which a sample of blood is drawn and checked for the following:
  • The number of red blood cells and platelets.
  • The number and type of white blood cells.
  • The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.
  • The portion of the sample made up of red blood cells.
  
• Peripheral blood smear: A procedure in which a sample of blood is checked for blast cells, the number and kinds of white blood cells, the number of platelets, and changes in the shape of blood cells.
• Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease.
• Bone marrow aspiration and biopsy: The removal of a small piece of bone and bone marrow by inserting a needle into the hipbone or breastbone. A pathologist views both the bone and bone marrow samples under a microscope to look for abnormal cells.

  The following tests may be done on the sample of tissue that is removed:

  • Cytogenetic analysis: A laboratory test in which the chromosomes of cells in a sample of bone marrow or blood are counted and checked for any changes, such as broken, missing, rearranged, or extra chromosomes. Changes in certain chromosomes may be a sign of cancer. Cytogenetic analysis is used to help diagnose cancer, plan treatment, or find out how well treatment is working. The cancer cells in myelodysplastic/myeloproliferative neoplasms do not contain the Philadelphia chromosome that is present in chronic myelogenous leukemia.
  • Immunocytochemistry: A laboratory test that uses antibodies to check for certain antigens (markers) in a sample of a patient’s bone marrow. The antibodies are usually linked to an enzyme or a fluorescent dye. After the antibodies bind to the antigen in the sample of the patient's bone marrow, the enzyme or dye is activated, and the antigen can then be seen under a microscope. This type of test is used to help diagnose cancer and to tell the difference between myelodysplastic/myeloproliferative neoplasms, leukemia, and other conditions.