What is lymphoma of the skin?
Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?
Lymphoma is a cancer that starts in cells called lymphocytes, which are part of the body’s immune system. The main types of lymphomas are:
- Hodgkin lymphoma (also known as Hodgkin’s lymphoma, Hodgkin disease, or Hodgkin’s disease)
- Non-Hodgkin lymphoma (also known as non-Hodgkin’s lymphoma, NHL, or sometimes just lymphoma), which includes all other lymphomas, including all skin lymphomas
Lymphocytes are in the lymph nodes (small, bean-sized collections of immune cells throughout the body) and other lymphoid tissues (such as the spleen, bone marrow, and some other organs, including the skin). Lymphomas can start in any of these places.
When a non-Hodgkin lymphoma starts only in the skin (not in other organs or tissues) it is called a skin lymphoma (or cutaneous lymphoma). A lymphoma that starts in lymph nodes or another part of the body and then spreads to the skin is not a skin lymphoma (because it didn’t start there).
The lymph system and lymphoid tissue
To understand what lymphoma is, it helps to know about the body’s lymph system.
The lymph system (also known as the lymphatic system) is made up of lymphoid tissue (see below), lymph vessels, and a clear fluid called lymph. Lymphoid tissue is found throughout the body and contains several types of immune system cells that work together to help the body fight infections.
Most of the cells in lymphoid tissue are lymphocytes, a type of white blood cell. The main types of lymphocytes are:
- B lymphocytes (B cells): B cells normally help protect the body against germs (bacteria or viruses) by making proteins called antibodies. The antibodies attach to the germs, marking them for destruction by other parts of the immune system.
- T lymphocytes (T cells): There are several types of T cells, each with a special job. Some T cells help protect the body against viruses, fungi, and some bacteria. For example, they recognize virus-infected cells and destroy them. T cells can also release substances called cytokines that attract other types of white blood cells, which then digest the infected cells. Some types of T cells help boost or slow the activity of other immune system cells.
Both types of lymphocytes can develop into lymphoma cells. In the skin, T-cell lymphomas are more common than B-cell lymphomas.
Doctors can tell B-cells and T-cells apart using lab tests that detect certain proteins on their surfaces and certain features of their DNA. These lab tests also can recognize several stages of B-cell and T-cell development. This can help doctors figure out which type of lymphoma a person has, which can help determine their treatment options.
Most lymphocytes are in lymph nodes. Lymph nodes are connected to each other by narrow tubes similar to blood vessels called lymphatics (or lymph vessels). Lymph vessels carry a colorless, watery fluid (lymph) that contains lymphocytes.
Along with the lymph nodes, lymphocytes can be found in the blood and in lymphoid tissues in many other places in the body, including the:
- Bone marrow (the soft, inner parts of certain bones)
- Adenoids and tonsils
- Digestive tract
- Other organs
Lymphomas can start in any part of the body that contains lymphoid tissue.
Some other types of cancer – lung or colon cancers, for example – can spread to lymph tissue such as the lymph nodes. But cancers that start in these places and then spread to the lymph tissue are not lymphomas.
Last Medical Review: 08/04/2014
Last Revised: 02/24/2016