Mycosis fungoides is the most common type of Cutaneous T-Cell Lymphoma (CTCL), a rare form of non-Hodgkin's lymphoma. The cause of mycosis fungoides remains unknown and there is no known cure. Unlike most non-Hodgkin's lymphomas, mycosis fungoides is caused by a mutation of T-cells. The malignant T-cells in the body initially migrate to the skin, causing various lesions to appear.
These lesions typically begin as what appears to be a rash and may progress to form plaques and disfiguring tumors. Early stage cases may be confused with other skin conditions until a definitive diagnosis is made based upon skin biopsy. Most cases of mycosis fungoides are early-stage and are diagnosed in patients over the age of 50.