Mycosis fungoides is a rare kind of skin cancer called cutaneous T-cell lymphoma (CTCL). Also called granuloma fungoides, this skin disease may look like a fungal rash but is not caused by a fungus.

Mycosis fungoides is a chronic condition that can slowly worsen over time. Like other cancers, it can spread to other parts of the body in later stages, like the digestive system, liver, or brain.

Mycosis fungoides is a life threatening condition. Early diagnosis and treatment are important for the best health outcomes.

Read on to learn more about this rare skin disease and what to do if you think you may have mycosis fungoides.

Doctors are not sure about the exact causes of mycosis fungoides and other types of T-cell lymphomas. Mycosis fungoides may begin when T cells change or mutate and turn into cancer cells. T cells or T lymphocytes are white blood cells that usually help the immune system protect the body.

It’s not known what causes T-cells to change. Some studies found that certain bacteria, viruses, or chemicals from the environment may play a role in causing mycosis fungoides.

In a 2020 study of people with Sézary syndrome (a related kind of T-cell lymphoma), researchers found that overgrowth of a common bacteria type that lives on the skin called staphylococcus aureus (S. aureus) may trigger T-cell changes in some cases.

People in this study showed improvement in symptoms when they took antibiotic medication that reduced this bacteria type.

Genetics and other factors may also increase the risk of getting mycosis fungoides. Some types of genetic or chromosomal mutations may increase the risk of getting this skin disease. A clinical study found that 18 percent of patients with mycosis fungoides or Sezary syndrome had the same genetic mutations.

What is Sézary syndrome?

Sézary syndrome is a related condition where irregular T cells from the skin make their way into the blood, according to 2019 research. This sometimes happens in late-stage mycosis fungoides, but people with Sézary syndrome tend to have these cells in the early stages as well.

Sézary syndrome is a more aggressive form of T-cell lymphoma. Its main feature is erythroderma, which is skin redness that covers the whole body. In its early stages, it can look like eczema.

In addition to erythroderma, people with Sézary syndrome may have:

  • soreness
  • swelling over much of their body
  • severe itching

Symptoms of mycosis fungoides can look like symptoms of some common and less serious skin conditions, like eczema or psoriasis.

Since mycosis fungoides usually worsens very slowly, it may look like a skin rash or scaly patch of skin for years or even decades. Because of this, people with this skin cancer may at first be misdiagnosed as having another skin condition.

If you have mycosis fungoides, your symptoms will vary depending on the stage you are in. At the start, mycosis fungoides may look like a sunburn or rash. It typically begins on an area of the skin that does not get much sun, like your back, belly, chest, buttocks, or upper thighs.

The color of skin lesions may also vary from red to purple or brown, depending on your skin tone. You may have:

  • skin redness or irritation
  • rash or red to brown or purple lesions
  • white, light brown, or tan spots or lesions
  • scaly or shiny patches
  • flat skin lesions
  • thicker or raised plaques
  • large skin nodules

The rash will eventually turn into flat, scaly patches that may look like common skin conditions such as eczema or psoriasis. In some people, this stage may look like light spots. This is more common in children, teenagers, and people with darker skin tones.

Patches eventually thicken and raise to become plaques that may look like thicker skin or welts. These plaques may also be itchy and resemble other common and less-serious skin conditions.

Later stage mycosis fungoides can cause more severe skin symptoms as the cancer spreads into the body. This can result in:

  • skin rash
  • scaly patches
  • raised plaques
  • sore-like tumors or growths on the skin

Later stage mycosis fungoides that has turned into Sézary syndrome may lead to:

  • widespread skin color changes
  • swelling
  • peeling
  • severe itching
  • thicker skin on the palm of the hands and soles of the feet

In the late stages of mycosis fungoides, there may be a general feeling of illness as the condition spreads throughout the body. Symptoms include:

  • severe fatigue
  • weakness
  • difficulty swallowing
  • coughing
  • fever
  • anemia
  • weight loss

In the late stages, your digestive and heart systems may also be affected. If the tumor cells reach the brain, vision may become blurred.

Doctors break mycosis fungoides into stages depending on how much the skin disease has progressed and what other organs are affected. These stages are:

  • Stage 1. Your skin has patches or plaques, but nothing has spread to your blood, lymph nodes, or other organs.
    • 1A. Patches or plaques cover less than 10 percent of your body.
    • 1B. Patches or plaques cover 10 percent or more of your body.
  • Stage 2. In addition to patches or plaques on your skin, your lymph nodes are enlarged but not cancerous.
    • 2A. There are no tumors on your skin.
    • 2B. There are one or more tumors on your skin.
  • Stage 3. More than 80 percent of your skin is affected by redness, patches, plaques, or tumors. Your lymph nodes may be enlarged, but they’re not cancerous.
    • 3A. No cancer cells are in your blood.
    • 3B. A low number of cancerous cells may be in the blood.
  • Stage 4. In addition to most of your skin being affected, you either have a high number of Sézary cells or the cancer has begun to spread.
    • 4A1. Your lymph nodes are enlarged but not cancerous. You also have a high number of Sézary cells in your blood.
    • 4A2. You may have cancer in your lymph nodes, but it has not spread to other parts of your body.
    • 4B. Cancer has spread to other organs, like the liver or spleen.

You may need several tests before a doctor can diagnose you with mycosis fungoides. These include:

  • physical exams
  • skin biopsies, where doctors examine a small sample of your skin
  • lymph or tissue biopsies
  • blood tests

In some cases, this skin condition will not show up in a skin biopsy or blood test. A doctor will need to perform more tests.

Specialized tests may look at T cells in the blood and use CT scans to look at the organs. A doctor may also recommend a genetic test.

Similar tests can also help a doctor understand what stage of mycosis fungoides you may have.

Treatment for mycosis fungoides depends on the stage of this disease. There are currently more than 30 different types of therapies with more currently undergoing trials. Some treatments help control symptoms like skin soreness, swelling, and itching.

Standard therapies and management for earlier stages of this skin condition mainly involve topical (skin) therapies such as:

The goals of later-stage treatments for mycosis fungoides are to shrink tumors and slow the spread of cancer cells. Treatment may involve both internal and external treatment, including:

Some therapies and medications for mycosis fungoides and other types of cancers can cause serious side effects that may limit how much treatment you receive.

There is currently no cure for mycosis fungoides. However, this skin condition is slow-growing, and your outlook depends on the stage and treatment.

Almost 70 percent of people with mycosis fungoides are at the early stage when a doctor diagnoses them. This means there’s a higher chance that treatment will be effective with positive health outcomes.

Survival rates for people with mycosis fungoides vary and depend on its stage at diagnosis and treatment. According to a 2020 review of studies, the 5-year survival rates for people with mycosis fungoides by stage were:

  • Stage 1B: 85.8 percent
  • Stage 2B: 62.2 percent
  • Stage 3A: 59.7 percent
  • Stage 3B: 54.0 percent
  • Stage 4A1: 52.5 percent
  • Stage 4A2: 34.0 percent
  • Stave 4B: 23.3 percent

Most treatments have some side effects that may cause changes to your lifestyle and overall health.

While still extremely rare, mycosis fungoides is twice as common in men than in women.

It is also more likely to happen in people 40 years or older.

While most people with mycosis fungoides are white, the incidence rate is higher among Blacks. According to a 2019 article, those who identified as Black or African American also experienced earlier onset and poorer outlook. The reasons for this racial disparity are not well understood.

Is mycosis fungoides contagious?

Mycosis fungoides is not contagious and cannot spread from person to person.

Is mycosis fungoides hereditary?

Mycosis fungoides is not known to be hereditary. There is a common gene mutation found in some people with mycosis fungoides, but it is not likely to be inherited or passed down in families.

How quickly does mycosis fungoides spread?

This type of cutaneous lymphoma is very slow-growing. In some cases, it can take some time to make an accurate diagnosis.

Mycosis fungoides is a rare type of cutaneous T-cell lymphoma that begins on the skin and can spread to the body through the lymph nodes.

While there is currently no cure for this type of skin cancer, it is slow-growing, especially in the early stages. Various types of treatments can help alleviate symptoms and manage this skin condition.

Diagnosis can be difficult because mycosis fungoides often looks like other common skin conditions like eczema and psoriasis. Contact a doctor right away if you notice any rashes on your skin or think you may have this skin condition.