ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to B-Cell Leukemia. To see other pages, use the menu on the side of your screen. Think of that menu as a roadmap to this full guide.
Leukemia is a cancer of the blood cells. Leukemia begins when healthy blood cells change and grow uncontrollably. Blood cells are made in the bone marrow, the spongy tissue inside the larger bones in the body. There are different types of blood cells, including red blood cells that carry oxygen throughout the body, white cells that fight infection, and platelets that help the blood to clot. Types of leukemia are named after the specific blood cell that becomes cancerous, such as the lymphoid cells or myeloid cells. Lymphoid cells are white blood cells mostly found in the lymphoid tissues, such as the spleen, lymph nodes, and tonsils. Myeloid cells are found in the bone marrow and develop into cells that fight bacterial infections. There are four main types of leukemia in adults:
- Acute lymphocytic leukemia (ALL) 
- Chronic lymphocytic leukemia (CLL) 
- Acute myeloid leukemia (AML) 
- Chronic myeloid leukemia (CML) 
About PLL and HCL
There are other, less common types of leukemia, but they are generally subcategories of one of the four main categories. This section focuses on prolymphocytic leukemia (PLL) and hairy cell leukemia (HCL), both of which are types of chronic B-cell leukemia. B cells are a specific type of lymphocyte that make antibodies for the immune system.
In PLL, many immature lymphocytes, or prolymphocytes, are found in the blood. This type of leukemia may occur by itself, together with CLL , or CLL may turn into PLL. PLL tends to worsen more quickly than CLL.
HCL is a slow-growing form of leukemia. It is called “hairy cell” because the abnormal lymphocytes have projections that look like hair when seen under a microscope. As these cells multiply, they build up in the bone marrow, blood, and spleen. Because these lymphocytes are abnormal, they do not fight disease and infection, and eventually may crowd out the healthy cells. Treatment is usually very effective for HCL.
Looking for More of an Overview?
If you would like additional introductory information, explore these related items on Cancer.Net. Please note these links will take you to other sections on Cancer.Net:
- ASCO Answers Fact Sheet : Read a one-page fact sheet (available as a PDF) that offers an easy-to-print introduction to CLL.
- Cancer.Net Patient Education Video : View a short video led by an ASCO expert in leukemia that provides basic information and areas of research.
The next section in this guide is Statistics  and it helps explain how many people are diagnosed with this disease and general survival rates. Or, use the menu on the side of your screen to choose another section to continue reading this guide.