Mycosis Fungoides

Mycosis fungoides is a type of skin lymphoma (cancer) that affects your body’s T-cells. It occurs when these white blood cells become cancerous. Often, a skin rash is the first sign of mycosis fungoides. It doesn’t have a cure, but many people who receive timely treatment experience long periods with no symptoms.


Illustrations showing the patch, plaque and tumor phases of mycosis fungoides on both light and dark skin.
Patchy dry skin, irregularly shaped plaques and raised tumors are all skin changes that can happen with mycosis fungoides.

What is mycosis fungoides?

Mycosis fungoides (pronounced “my-KOH-sis fun-GOY-deez”) is a blood cancer that happens when white blood cells called T-cells transform into malignant (cancer) cells. T-cells are a kind of lymphocyte. Lymphocytes fight harmful pathogens in your body, like viruses and bacteria. With mycosis fungoides, T-cells transform into cancer cells that affect your skin.

Mycosis fungoides is a type of cutaneous T-cell lymphoma (CTCL). CTCL is a group of rare blood cancers that cause changes in your skin, like itchiness, rashes, plaques or tumors.

Although mycosis fungoides affects your skin, it’s not a form of skin cancer because your T-cells — not skin cells — become cancerous.


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Symptoms and Causes

What are the symptoms of mycosis fungoides?

Mycosis fungoides symptoms occur in several stages of skin changes. Not everyone progresses through all the phases. Some may happen simultaneously.

For many people, the first sign of disease in the early stage is a mycosis fungoides rash. Mycosis fungoides stages include:

  • Premycotic phase:A scaly skin rash forms. It appears on parts of your body not usually exposed to the sun, like your lower belly, thighs, butt and breasts (chest).
  • Patch phase:The skin around the rash becomes thin. It may be itchy and dry, like eczema.
  • Plaque phase:Your skin forms small, raised bumps or hard bumps.
  • Tumor phase:Tumors, raised areas of skin that penetrate more deeply than plaques, form on your skin. The most common locations include your thighs, groin, armpits and the inside of your elbow. The tumors may develop ulcers and get infected.

In the most severe stages, many cancerous T-cells circulate in your blood. At this point, they’re called Sézary cells. High levels of Sézary cells may cause mycosis fungoides to evolve into Sézary syndrome. With this condition, you may develop a red rash all over your body, called erythroderma.

What causes mycosis fungoides?

Experts don’t know what causes mycosis fungoides, but genetic mutations may play a role. Genetic mutations are changes in the genetic material inside a cell, like DNA or chromosomes. Many people with mycosis fungoides have missing genetic material or errors in the genetic material inside the cells that become malignant.

These genetic mutations don’t seem to be inherited (passed down through families).

Researchers continue to study other potential causes, such as exposure to certain environmental toxins and infections.

Is mycosis fungoides contagious?

Mycosis fungoides isn’t contagious. It doesn’t spread from person to person.


Diagnosis and Tests

How is mycosis fungoides diagnosed?

It may be challenging to diagnose mycosis fungoides based on a visual skin exam because it can resemble other skin conditions. It’s easy to mistake mycosis fungoides for more common skin conditions during an exam, like eczema or psoriasis.

To confirm or rule out mycosis fungoides, your healthcare provider will likely perform additional tests such as:

  • Skin biopsy or lymph node biopsy: A procedure that removes tissue from the affected area so a pathologist can test the tissue in a lab for signs of mycosis fungoides. You may need multiple biopsies to locate evidence of the tumor cells associated with mycosis fungoides.
  • Blood tests: Your healthcare provider may look for changes in your blood cells and chemical markers (like enzymes) that may be signs of mycosis fungoides.
  • Imaging procedures: Your healthcare provider may look for signs that the cancer has spread to your lymph nodes or organs other than your skin. Imaging procedures may include a CT scan or PET scan.

How do doctors stage mycosis fungoides?

Cancer staging is an important part of a mycosis fungoides diagnosis. Cancer staging classifies mycosis fungoides on a scale from I to IV based on how invasive it is and the extent it’s spread. Knowing the stage helps your healthcare provider determine treatments.

Stages IA through IIB are regarded as early-stage mycosis fungoides. Stages IIB through IVB are considered advanced disease.

When staging mycosis fungoides, providers consider various factors, including:

  • The size of skin lesions (patches, plaques and tumors).
  • How much of your skin contains skin lesions.
  • Whether the cancer has spread to your lymph nodes.
  • Whether the cancer has spread to your bloodstream.
  • Whether the cancer has spread to organs other than your skin.

Management and Treatment

How is mycosis fungoides treated?

Mycosis fungoides treatment depends on the cancer stage and type of skin changes. Many treatment options focus on relieving symptoms and improving your quality of life.

Your healthcare provider may prescribe:

  • Skin-directed therapy: Topical gels, steroids, retinoids or ultraviolet (UV) light (phototherapy) treat cancer on affected areas of your skin. With psoralen-ultraviolet A therapy (PUVA), a healthcare provider combines a pill (psoralens) with UV light to destroy cancer cells on your skin. Your provider may also use a topical chemotherapy drug, such as mechlorethamine (Valchlor®).
  • Systemic therapy:Medicines such as bexarotene (Targretin®) or methotrexate (Rheumatrex®, Trexall®) can treat your whole body. Other classes of drugs include Interferon α and histone deacetylase (HDAC) inhibitors. Intravenous medicines (taken through your vein) include chemotherapy, such as gemcitabine (Gemzar®), pegylated liposomal doxorubicin or pralatrexate (Folotyn®).
  • Immunotherapy:Immunotherapy boosts your immune system so it’s better at identifying and attacking cancer cells.
  • Monoclonal antibodies as targeted therapy:These medicines detect and destroy cancer cells. Healthcare providers may use targeted therapy if your body hasn’t responded to other systemic therapy. Treatments include mogamulizumab-kpkc (POTELIGEO®) and brentuximab vedotin (Adcetris®).
  • Radiation therapy:With radiation therapy, strong beams of energy from outside your body destroy cancer cells or stop their growth.

Healthcare providers rarely use traditional chemotherapy for mycosis fungoides. Chemotherapy doesn’t always effectively treat mycosis fungoides. It also carries a significant risk of side effects.

Is there a cure for mycosis fungoides?

There isn’t a cure for mycosis fungoides. Although there’s no way to get rid of it completely, with early diagnosis and treatment, people often live for many years without symptoms. Most live a normal life span.


How can I reduce my risk of mycosis fungoides?

There’s no proven way to prevent mycosis fungoides. You can reduce the risks of late-stage mycosis fungoides by scheduling regular appointments with a healthcare provider. Regular checkups can increase the chances of detecting mycosis fungoides in its early stages.

Perform monthly skin self-checks for rashes, moles or other changes. If you notice any skin changes, schedule an appointment with a dermatologist.

Outlook / Prognosis

What is the outlook for people with mycosis fungoides?

Your prognosis depends on multiple factors, with cancer stage being especially important.

It’s much easier to treat mycosis fungoides in its early stages. Many people who receive early diagnosis and treatment experience long periods with no symptoms.

More advanced mycosis fungoides may need more intensive treatment. For example, you may need radiation therapy or chemotherapy if cancer has spread beyond your skin.

What is the life expectancy of someone with mycosis fungoides?

The 10-year survival rate for early-stage mycosis fungoides is 95%. The life expectancy for advanced mycosis fungoides is three to five years, and it may be less if the cancer has spread beyond your skin.

Still, it’s important to remember that these numbers are just statistics. Your prognosis depends on various factors unique to you, including age, overall health and disease course. Your healthcare provider is your best resource for answering questions about what to expect with mycosis fungoides, including likely treatment outcomes and life expectancy.

Living With

What questions should I ask my doctor?

Questions to ask include:

  • What are my treatment options?
  • Are there any side effects of mycosis fungoides treatment?
  • What’s the risk that mycosis fungoides will return after treatment?
  • What happens if I decide not to treat it?
  • How can I lower my chances that mycosis fungoides will return?
  • What resources are available for me to care for myself during treatment?

Additional Common Questions

How common is mycosis fungoides?

Mycosis fungoides is rare. Healthcare providers diagnose around 3,000 people with cutaneous T-cell lymphomas each year. On average, about 70% of all cutaneous T-cell lymphomas are mycosis fungoides. Because mycosis fungoides progresses slowly, more people may have the condition without knowing it.

Mycosis fungoides can affect people of all ages, but it’s most common in adults over 50. Men and people assigned male at birth (AMAB) are twice as likely as women and people assigned female at birth (AFAB) to develop mycosis fungoides. People who are Black are more likely to develop this condition than people who are white.

What is the difference between mycosis fungoides and Sézary syndrome?

Mycosis fungoides occurs when T-cell lymphocytes become cancerous. When these cancerous T-cells circulate in your blood, they’re called Sézary cells.

Sézary syndrome occurs when you have large numbers of T-cells — called Sézary cells — in your blood that can go to your skin and lymph nodes.

What triggers mycosis fungoides?

Scientists haven’t identified a single cause that triggers mycosis fungoides. They’ve identified common changes in specific chromosomes, including missing genetic material and genetic material with errors, within the cancer cells. These changes develop over a person’s lifetime (acquired).

What does mycosis fungoides look like on the skin?

One of the challenges of diagnosing mycosis fungoides is that it doesn’t look the same on everyone. Also, in the early stages, it often resembles common skin conditions, like eczema and psoriasis.

Depending on the stage, it may look like a rash, raised and discolored skin or bumps that may develop sores. Most often, these skin changes occur on your body in places protected from sun exposure.

A note from Cleveland Clinic

For many people, the first sign of mycosis fungoides is a skin rash that’s otherwise symptom-free. Although it’s a blood cancer, it’s easy to mistake for common skin conditions. This is why it’s so important to have a dermatologist check any skin changes. Early diagnosis and treatment can make all the difference regarding your prognosis. Many people who receive treatment early experience years with no symptoms.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 05/12/2023.

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