Leukemias are classified by how quickly they progress and by the type of cell involved.

In acute leukemia, immature white blood cells, known as blasts, grow too rapidly. This can cause severe symptoms right away.

In chronic leukemia, abnormal cells grow more slowly and symptoms may not appear for years.

Leukemia affects two types of cells:

  • Myeloid leukemias develop in white blood cells known as neutrophils and monocytes that help fight bacterial or fungal infections.
  • Lymphocytic leukemias develop in B lymphocytes, T lymphocytes, or natural killer (NK) cells that produce antibodies or other substances to fight infections.

There are four main types of leukemia: