Leukemia is a cancer of the blood cells. Leukemia begins when healthy blood cells change and grow out of control.
About blood cells
Blood cells are made in the bone marrow, the spongy tissue inside the larger bones in the body. Changes in the bone marrow cells can cause too many or too few of certain blood cells. There are different types of blood cells:
- Red blood cells that carry oxygen throughout the body
- White blood cells that fight infection
- 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 a type of white blood cell. Myeloid cells are bone marrow cells that turn into the cells that fight bacterial infections.
There are 4 main types of leukemia in adults:
- Acute lymphocytic leukemia (ALL)
- Chronic lymphocytic leukemia (CLL)
- Acute myeloid leukemia (AML)
- Chronic myeloid leukemia (CML)
There are also less common types of leukemia, but they are generally subcategories of 1 of the 4 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.
Subtypes of T-cell leukemia
The subtypes of T-cell leukemia include:
- Large granular lymphocytic leukemia (LGLL). LGLL is a slow-growing T-cell leukemia. It is more common in women than in men. The cause of LGLL is unknown. However, about 30% of people with LGLL also have rheumatoid arthritis. Rheumatoid arthritis is a chronic disease causing swelling in the joints of the hands, feet, wrists, knees, hips, or shoulders. Also, nearly half of patients with LGLL have a genetic change in either a gene called STAT3 or another called STAT5B.
- T-cell prolymphocytic leukemia (T-PLL). T-PLL is an aggressive subtype of CLL. It is the most common mature T-cell leukemia in adults. T-PLL 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). Patients with T-PLL often have genetic changes to their T-cells called a T-cell receptor rearrangement, which is linked to abnormal T-cell growth. This type of genetic change occurs from damage to the genes during a person’s life. It is not passed from parent to child.
- Adult T-cell leukemia/lymphoma (ATLL). ATLL has 4 subtypes. Depending on the different features, it is subclassified as smoldering, chronic, acute, or adult T-cell lymphoma. Lymphoma is a 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 only on the skin. Sezary syndrome is usually slow-growing and takes years to develop from mycosis fungoides. Sezary syndrome is generally diagnosed when large numbers of the lymphoma cells are found in the blood, often together with reddening of the skin, which is called erythroderma.