Mycosis fungoides is a type of lymphoma.
Lymphomas are blood tumors.
In mycosis fungoides the blood lymphoma stays mostly in the skin. This results in a rash. Most people who have mycosis fungoides will have the rash over many years. It is very difficult to determine if someone has mycosis fungoides, usually several biopsies are required over a number of years before the diagnosis can be made. Must people who have mycosis fungoides have it for years.