Leukemia is cancer of the bone marrow, which is the organ responsible for blood cell development. Bone marrow is the soft, inner part of the bones and is made up of blood, stem cells, and tissues that support bone growth.

Normally, there are three types of cells in your blood stream:

  • White blood cells
  • Red blood cells
  • Platelets

In patients with leukemia, immature cells called "blasts" overtake their healthy bone marrow. In the normal state, blasts are very rare, and divide and become mature white blood cells, red blood cells, and platelets.

Leukemia can be acute (rapidly progressing) or chronic (slow growing), lymphoid or myeloid. Lymphoid cells are cells that, under normal development, would have become lymphocytes, types white blood cells.

Myeloid cells are cells that would have become other blood cells (white blood cells other than lymphocytes, red blood cells or platelets) under normal development.

Penn Medicine has one of the few hematologic malignancy (leukemia, lymphoma and myeloma) research programs in the country that is approved and funded by the National Cancer Institute. It is through this research program that Penn has made significant advances in improving bone marrow and stem cell transplants.