Leukemia is a cancer of the blood cells. Blood cells (including red cells that carry oxygen, white cells to fight infection, and platelets that cause blood to clot) are produced in the bone marrow, the spongy tissue inside the larger bones in the body. Abnormalities in the bone marrow cells can cause the overproduction or underproduction of certain blood cells. Types of leukemia are named after the specific blood cell that becomes cancerous, such as the lymphocytic cells (white blood cells of the immune system) or the myeloid cells (cells of the bone marrow, the spongy, red tissue in the inner part of large bones). There are four main types of leukemia in adults:
There are also other, less common types of leukemia, but they are generally subcategories of one of the four main categories. 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 participates in the immune system defenses.
Subtypes of T-cell leukemia
Large granular lymphocytic leukemia (LGLL). LGLL is a slow-growing leukemia of the T cells and is more common in women than in men. The cause of LGLL is unknown, although approximately 30% of people with LGLL also have rheumatoid arthritis (a chronic, progressive disease in which inflammatory changes occur throughout the connective tissues of the body, mostly 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 that has only been defined recently. It occurs more often in older men, but women may also be affected. It can affect the skin, but in a different way than Sezary syndrome (see below).
Adult T-cell leukemia/lymphoma (ATLL). ATLL has four clinical subtypes. Depending on the clinical 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 are rapidly progressing diseases. 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 limited to the skin. Sezary syndrome is generally diagnosed when large numbers of the lymphoma cells are found in the blood, often in association with erythroderma (reddening of the skin).
Statistics
In 2009, an estimated 44,790 people of all ages (25,630 men and 19,160 women) in the United States will be diagnosed with leukemia. Of these, an estimated 15,490 people (9,200 men and 6,290 women) will be diagnosed with CLL. T-cell leukemia is rare and the number of people diagnosed each year is much lower.
Cancer statistics should be interpreted with caution. These estimates are based on data from thousands of cases of this type of cancer in the United States each year, but the actual risk for a particular individual may differ. It is not possible to tell a person how long he or she will live with leukemia.
Statistics adapted from the American Cancer Society's publication, Cancer Facts and Figures 2009.
Find out more about basic cancer terms used in this section.
Last Updated: January 08, 2009
