What Is Mycosis Fungoides?

Mycosis Fungoides is a type of T-cell lymphoma (cancer of the lymph system) that affects the skin. T-cells are a type of white blood cell that are responsible for making antibodies that help fight infection. In mycosis fungoides, these T-cells become cancerous and cause the skin to develop lesions. This condition is often present for many years and slowly progresses over time.

Mycosis fungoides is the most common type of cutaneous T-cell lymphoma. There are about 3.6 cases per 1 million people diagnosed in the United States each year. 

This article will review the symptoms and causes of mycosis fungoides, as well as how it is diagnosed and treated. 

Mycosis Fungoides Symptoms

Symptoms of mycosis fungoides can differ as the disease progresses. It can take many years, if not decades, for the symptoms and skin changes to move through various stages. Mycosis fungoides is most often diagnosed in adulthood, although it is possible that it can develop during childhood. 

Stage 1

In the first stage, the first symptom is often itching or pain in the affected area. There may also be red patches present across the trunk or on the extremities. Patches are flat, not raised areas of skin. Oftentimes this initial stage is misdiagnosed as another skin disorder, such as eczema or psoriasis—especially in children.

Stage 2

This is the plaque stage. During this stage, thickened skin plaques form on the skin, often in an oval shape. They may develop individually but begin to grow into each other. 

Stage 3

This is the tumor stage. In this stage, larger, ulcerated nodules develop that can potentially be large in size. They may be red-brown or even bluish in color.

Stage 4

In this stage, cancer cells spread throughout the body. Symptoms noted during this stage can include:

• Fatigue
• Weakness
• Fever
• Low red blood cells (anemia)
• Unexplained weight loss
• Coughing
• Shortness of breath
• Difficulty swallowing
• Headaches
• Vision changes

Mycosis Fungoides vs. Sézary Syndrome

There is another type of cancer very closely related to mycosis fungoides called Sézary syndrome. In this other, aggressive type of cutaneous T-cell lymphoma, in addition to the skin being affected with cancerous T-cells, the cancerous cells are also present in the lymph nodes and the blood.

Causes

There is no known cause for mycosis fungoides. Research is currently ongoing to determine the cause by investigating genetic mutations inside the cancer cells. Genetic mutations have the potential to alter a person's DNA and cause cancer cells to form.

There are some findings to suggest that certain HLA genes (genes that help the immune system tell the difference between cells made in the body and foreign cells) may play a role in developing mycosis fungoides.

Diagnosis

In the initial stages of the disease, it may be difficult for a diagnosis of mycosis fungoides to be made, as it often resembles other, mostly benign (noncancerous) skin disorders. Some of these skin conditions may include:

• Discoid lupus erythematosus (a form of the autoimmune disease lupus)
• Eczema (inflammatory skin condition that causes a dry, scaly, itchy rash)
• Leprosy (a rare bacterial infection that causes skin lesions)
• Lichen planus (an immune-mediated disease that causes an itchy rash, often inside of the mouth)
• Benign lymphocytic infiltrates (a rare condition in which a buildup of white blood cells presents as lesions or lumps on the skin)
• Chronic Lymphocytic Leukemia (a slow-growing cancer that starts in the bone marrow)
• Parapsoriasis lichenoides chronica (a rash made up of scaly plaques)

A physical skin exam is important to document the location and appearance of all skin lesions. For a final diagnosis, however, a skin biopsy must be done.

During a skin biopsy, a sample of tissue is removed from a skin lesion and inspected under a microscope to look for cancerous cells. Other tests that may be needed include:

• Flow cytometry: This test uses a special method of sampling tissue stained with dye through a beam of light. It helps determine certain characteristics of the cells and can evaluate for leukemias (cancers of the blood) or lymphomas.
• Immunohistochemistry: This test can determine what the cancer cells are made of by using special dyes to test for antigens and antibodies on the cells' surface. 
• T-cell receptor gene rearrangement: This test evaluates the appearance of genes responsible for making T-cells. 

Treatment

A variety of treatment options exist for mycosis fungoides and depend on the stage of the condition. 

Phototherapy

During phototherapy, beams of either ultraviolet A (UVA) or ultraviolet B (UVB) light are directed toward the skin, to help treat the areas of concern. Limiting time in direct sunlight is typically recommended when being treated with phototherapy.

Topical Treatments

Many topical medications may be used to treat the skin affected by mycosis fungoides. These treatments may include:

• Steroid creams or ointments
• Retinoids, which are derived from Vitamin A
• Mechlorethamine gel, a prescription cream specifically for stage 1 mycosis fungoides

Medications

A variety of medications, taken either in pill form, by injection, or through intravenous (IV) infusion, may be used to treat mycosis fungoides, including the following: 

• Retinoids: These medications that are derived from Vitamin A can can be taken by mouth or topically (on the skin).
• Lenolidaminde: This oral medication affects how the tumors receive their blood supply and can kill abnormal cells. 
• Chemotherapy: Typically given through IV, these medications are used to kill cancer cells by stopping them from dividing. 
• Immunotherapy: These infusions allow the immune system to see the abnormal cancer cells and attack them. 
• Monoclonal antibodies: A type of immunotherapy, these medications (Brentuximab, Mogamulizab) target certain proteins on the outside of the cancer cells to alert the immune system to destroy them. These are given through infusion.

Other Treatments

Other treatments for mycosis fungoides may be received by enrolling in a clinical trial. In clinical trials, investigative medications are studied to see if they are effective at treating a disease. 

Another treatment sometimes used is a stem cell transplant. During this process, high doses of chemotherapy and sometimes radiation therapy (using high doses of radiation) are given to kill abnormal cells and replace them with healthy cells, either from the same person or from a donor.

Prognosis 

Mycosis fungoides is considered to be an indolent lymphoma, meaning it grows and progresses very slowly over time. The ultimate prognosis depends upon the stage of the cancer.

In early stage 1 disease, patients who have been getting treatment are likely to have a normal life expectancy. Life expectancy decreases as the disease progresses, with people with stage 3 disease having a 10-year survival rate of 83%. If the cancer spreads into other areas of the body, the 10-year survival rate decreases to about 20%.

Coping 

Experiencing the skin changes related to mycosis fungoides and having a diagnosis of cancer can be distressing. Seeking support from your healthcare team on how to manage symptoms and treatment-related side effects is important. Finding support from family, friends, or through formal support groups or counseling can help someone deal with the feelings associated with this disease. 

A Word From Verywell

If you’re concerned about any skin lesions you may have, especially ones that aren’t improving with treatment and time, reach out to your healthcare team for evaluation.

Receiving a cancer diagnosis can be distressing, but it is very possible to have a long life with mycosis fungoides, as it is slow growing, taking many years to progress. Getting treatment when needed and sticking to the treatment plan prescribed by your healthcare team are important to getting the best outcome possible. Seek out support from family and friends or others to help manage the stress and feelings that come with this diagnosis.

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