Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Cutaneous T-cell Lymphomas

(Mycosis Fungoides; Sézary Syndrome)


Peter Martin

, MD, Weill Cornell Medicine;

John P. Leonard

, MD, Weill Cornell Medicine

Last full review/revision Jul 2020| Content last modified Jul 2020
Click here for the Professional Version
Topic Resources

Cutaneous T-cell lymphomas (CTCL) are a rare, persistent, very slow-growing type of non-Hodgkin lymphoma.

Lymphomas (see also Overview of Lymphoma) are cancers of a specific type of white blood cells known as lymphocytes. These cells help fight infections. Lymphomas can develop from either B or T lymphocytes. T lymphocytes are important in regulating the immune system and in fighting viral infections. B lymphocytes produce antibodies, which are essential in fighting off some infections.

The most common types of CTCL are

  • Mycosis fungoides

  • Sézary syndrome

Most people who develop CTCL are older than 50. It originates from mature T cells (T lymphocytes) and first affects the skin.

Mycosis fungoides starts so subtly and grows so slowly that it may not be noticed initially. It causes a long-lasting, itchy rash—sometimes a small area of thickened, itchy skin that later develops nodules and slowly spreads. In some people, it develops into a form of leukemia (Sézary syndrome). In other people, it progresses to the lymph nodes and internal organs. Even with a biopsy, doctors have trouble diagnosing this disease in its early stages. However, later in the course of the disease, a biopsy shows lymphoma cells in the skin.

Sézary syndrome also starts subtly and grows slowly. It causes the skin to become red all over the body with cracking of the palms and soles. Lymph node enlargement is usually mild. In addition to the rash, people may also have symptoms of fever, night sweats, and weight loss. As with mycosis fungoides, doctors have trouble diagnosing this disease in its early stage even with a skin biopsy. A blood smear (where a drop of blood is examined under a microscope) may show Sézary cells (malignant T cells with a characteristic appearance) and this can help make the diagnosis in addition to a skin biopsy.

Treatment of CTCL can be divided into

  • Therapy directed at the skin, such as light therapy (phototherapy) or topical drugs

  • Bodywide therapy, such as chemotherapy or targeted drugs, usually given intravenously

Therapy directed at the skin is usually started first and is often effective for years. This type of treatment includes medicated creams such as corticosteroids or retinoids applied to the skin, or a form of radiation therapy called electron beam therapy or with sunlight (phototherapy).

Chemotherapy is given if skin-directed therapy has failed or in people with CTCL that has spread beyond the skin.

More Information

The following is an English-language resource that may be useful. Please note THE MANUAL is not responsible for the content of this resource.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Test your knowledge

Chronic Lymphocytic Leukemia (CLL)
Chronic lymphocytic leukemia (CLL) is a generally slow-growing blood disorder. In CLL, lymphocytes (small white blood cells found mostly in the lymph system) become cancerous. Gradually, these cancerous cells replace normal cells. More than three-quarters of people with CLL belong to one age group. Which of the following is that age group?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID