What is lymphoma of the skin?
Lymphoma is a cancer that starts in cells called lymphocytes, which are part of the body’s immune system. Lymphocytes are in the lymph nodes and other lymphoid tissues (such as the spleen, bone marrow, and some other organs, including the skin).There are 2 main types of lymphomas.
- 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 contains all other lymphomas, including all skin lymphomas
When a non-Hodgkin lymphoma starts only in the skin (not 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 considered a skin lymphoma (because it didn’t start there).
Hodgkin and non-Hodgkin lymphomas differ in how they behave, spread, and respond to treatment. Doctors can usually tell the difference between them by looking at the cancer cells under a microscope. In some cases, sensitive lab tests may be needed to tell them apart.
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, 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 2 main types of lymphocytes are B lymphocytes (B cells) and T lymphocytes (T cells).
B lymphocytes: B cells normally help protect the body against germs (bacteria or viruses) by making proteins called antibodies. The antibodies attach to the germs and attract other immune system cells that then surround and digest the antibody-coated germs. Antibodies also attract certain blood proteins that can kill bacteria.
T lymphocytes: There are several types of T cells, each with a specialized 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. Overall, B-cell lymphomas are much more common than T-cell lymphomas in the United States. In the skin, though, T-cell lymphomas are more common than B-cell lymphomas. Different types of lymphoma can develop from each type of lymphocyte.
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. There are also several stages of B-cell and T-cell development that can be recognized by these lab tests.
This information is important because for each type of lymphoma, the cancer cells tend to resemble a particular type of normal lymphocyte at a certain stage of development. Figuring out the type of lymphoma a person has helps determine treatment options.
Most lymphocytes are in lymph nodes, which are small, bean-sized collections of immune cells throughout the body. 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, collections of lymphocytes can be found in many other places in the body, including the:
- Bone marrow
- 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: 03/14/2013
Last Revised: 02/11/2014