Cancer is a group of many related diseases. All cancers begin in
cells, the body's basic unit of life. Cells make up tissues, and tissues make up the organs of the body.
Normally, cells grow and divide to form new cells as the body needs them. When cells grow old and die, new cells take their place. Sometimes this orderly process goes wrong. New cells form when the body does not need them, and old cells do not die when they should. These extra cells can form a mass of tissue called a growth or
tumor.
Tumors can be benign or malignant.
Benign tumors are not cancer. Usually, doctors can remove them. Cells from benign tumors do not spread to other parts of the body. In most cases, benign tumors do not come back after they are removed. Most important, benign tumors are rarely a threat to life.
Malignant tumors are cancer. They are generally more serious. Cancer cells can invade and damage nearby tissues and organs. Also, cancer cells can break away from a malignant tumor and enter the bloodstream or the lymphatic system. That is how cancer cells spread from the original (
primary) tumor to form new tumors in other organs. The spread of cancer is called
metastasis.
Myelodysplastic Syndromes
Myelodysplastic Syndromes are diseases of the blood and bone marrow. The bone marrow makes blood
stem cells (immature cells) that develop into mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell. The lymphoid stem cell develops into a white blood cell. The myeloid stem cell develops into one of three types of mature blood cells. These are red blood cells that carry oxygen and other materials to all tissues of the body, white blood cells that fight infection and disease and platelets that help prevent bleeding and cause blood clots to form.
In myelodysplastic syndromes, 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 function normally and either die in the bone marrow or soon after they enter the blood. This leaves less room for healthy white blood cells, red blood cells, and platelets to develop in the bone marrow.
Myelodysplastic syndromes have too few or too many types of healthy blood cells in the bone marrow or blood.
They include the following diseases:
Refractory Anemia: There are too few red blood cells in the blood and the patient has anemia. The number of white blood cells and platelets is normal.
Refractory Anemia with Ringed Sideroblasts: There are too few red blood cells in the blood and the patient has anemia. The red blood cells have too much iron. The number of white blood cells and platelets is normal.
Refractory Anemia with Excess Blasts: There are too few red blood cells in the blood and the patient has anemia. Five percent to 19% of the cells in the bone marrow are blasts and there are a normal number of blasts found in the blood. There also may be changes to the white blood cells and platelets. Refractory anemia with excess blasts may progress to acute myeloid leukemia.
Refractory Anemia with Excess Blasts in Transformation: There are too few red blood cells, white blood cells, and platelets in the blood and the patient has anemia. Twenty percent to 30% of the cells in the bone marrow are blasts and more than 5% of the cells in the blood are blasts. Refractory anemia with excess blasts in transformation is sometimes called acute myeloid leukemia.
Refractory Cytopenia with Multilineage Dysplasia: There are too few of at least two types of blood cells. Less than 5% of the cells in the bone marrow are blasts and less than 1% of the cells in the blood are blasts. If red blood cells are affected, they may have extra iron. Refractory cytopenia may progress to acute leukemia.
Myelodysplastic Syndrome Associated with an Isolated del(5q) Chromosome Abnorality: There are too few red blood cells in the blood and the patient has anemia. Less than 5% of the cells in the bone marrow and blood are blasts. There is a specific change in the chromosome.
Unclassifiable Myelodysplastic Syndrome: There are too few of one type of blood cell in the blood. The number of blasts in the bone marrow and blood is normal, and the disease is not one of the other myelodysplastic syndromes.