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Leukemia is a cancer of the blood cells. Leukemia begins when normal 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 blood cells that fight infection, and platelets that help the blood to clot. Changes in the bone marrow cells can cause too many or too few of certain blood cells.
Types of leukemia are named after the specific blood cell that becomes cancerous, such as the lymphoid cells (a type of white blood cell) or the myeloid cells (bone marrow cells that turn 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 T-cell leukemia
There are also less common types of leukemia, but they are generally subcategories of one of the four main categories listed above. This section focuses on different types of chronic T-cell lymphocytic leukemia, a subtype of chronic lymphocytic leukemia (CLL). A T cell is a type of white blood cell that directly helps body’s immune system fight infection. The subtypes of T-cell leukemia include:
Large granular lymphocytic leukemia (LGLL). LGLL is a slow-growing T-cell leukemia and is more common in women than in men. The cause of LGLL is unknown, although about 30% of people with LGLL also have rheumatoid arthritis (a chronic disease causing swelling in the joints of the hands, feet, wrists, knees, hips, or shoulders).
T-cell prolymphocytic leukemia (T-PLL). T-PLL is an aggressive subtype of CLL. It is more common in older men, but women may also develop T-PLL. It can affect the skin, but in a different way than Sezary syndrome (see below).
Adult T-cell leukemia/lymphoma (ATLL). ATLL has four subtypes. Depending on the different features, it is subclassified as smoldering, chronic, acute, or adult T-cell lymphoma (cancer of the lymph system). The acute and the adult T-cell lymphoma subtypes grow quickly. ATLL is caused by a retrovirus called the human T-cell leukemia virus (HTLV1).
Sezary syndrome. Sezary syndrome is a form of mycosis fungoides, a T-cell lymphoma that occurs in the skin. Sezary syndrome is usually slow-growing and takes years to develop from mycosis fungoides, which is located only on the skin. Sezary syndrome is generally diagnosed when large numbers of the lymphoma cells are found in the blood, often together with reddening of the skin.
Find out more about basic cancer terms used in this section.
Looking for More of an Overview?
If you would like additional introductory information, explore these related items on Cancer.Net:
- ASCO Answers Fact Sheet: Read a one-page fact sheet (available in PDF) that offers an easy-to-print introduction for 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.
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