NCCN Guidelines for Patients® | Myeloproliferative Neoplasms

8 NCCN Guidelines for Patients ® : Myeloproliferative Neoplasms, 2018 You’ve learned that you have or may have a blood cancer. It’s common to feel shocked and confused. Part 1 reviews some basics that may help you learn about myeloproliferative neoplasms. Blood To learn about blood cancers, you first must know about blood. Blood is one of the fluids in the body. It consists of blood cells that move within plasma. Plasma is mostly water. Blood cells There are three main types of blood cells. One type is red blood cells (also called erythrocytes). Another type is white blood cells (leukocytes). The third type is platelets (thrombocytes). Blood cells have important jobs. Red blood cells carry oxygen throughout the body. White blood cells help fight germs. Platelets help control bleeding. Your blood cells don’t live forever. Many have a short lifespan. Thus, blood cells are being replaced in your body all the time. Blood cell formation Most blood cells are formed in bone marrow. Bone marrow is the sponge-like tissue in the center of most bones. See Figure 1 . Within your bone marrow are blood-forming cells. Blood stem cells are the cells from which all blood cells are formed. They are also called hematopoietic stem cells. As shown in Figure 2 , they start the family tree of blood cells. Blood stem cells can make exact copies of themselves. They can also make new cells that are a step closer to being a blood cell. These cells are called progenitor cells. Compared to stem cells, progenitor cells are set to become a certain type of blood cell. There are two types of blood progenitor cells. Lymphoid progenitor cells start one branch of the family tree. Myeloid progenitor cells start another branch. At the end of the lymphoid branch is a type of white blood cell called lymphocytes. There are three types of lymphocytes. They are NK cells, B-cells, and T-cells. Lymphocytes are released from bone marrow into the bloodstream. At the end of the myeloid branch are white blood cells, red blood cells, and platelets. These white blood cells are called granulocytes. Granulocytes include neutrophils, eosinophils, and basophils. Red blood cells, platelets, and granulocytes are released from bone marrow into the bloodstream. A disease of cells Your body is made of trillions of cells. Cancer is a disease of cells. Each type of cancer is named after the cell from which it is derived. MPNs ( m yelo p roliferative n eoplasms) are a group of rare blood cancers. They are cancers that derive from blood-forming stem cells within the myeloid branch. “Myelo” means marrow. “Proliferative” means growing and refers to making too many cells. A neoplasm is any abnormal growth. MPNs have too many blood-forming cells in the marrow. In turn, there are also too many blood cells. MDS ( m yelo d ysplastic s yndromes) are also cancers of blood-forming cells. However, the blood-forming 1 MPN basics Blood | A disease of cells