Normally, the bone marrow makes blood stem cells. These immature cells become mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell. A myeloid stem cell develops into one of three types of mature blood cells: a red blood cell, white blood cell, or platelet. A lymphoid stem cell becomes a white blood cell.

Myeloproliferative neoplasms (MPN) occur when the bone marrow, the spongy tissue inside the large bones in the body, makes too many blood cells.

These cancers are sorted based on which type of blood cell is overproduced: red blood cells, white blood cells, or platelets. Sometimes the body will make too many of more than one type of blood cell, but usually one type is affected more than the others.

There are several kinds of myeloproliferative neoplasms. These include polycythemia vera, myelofibrosis, essential thrombocythemia, and eosinophilia.

Learn more about treatment for myeloproliferative neoplasms.