Mycosis fungoides is the most common form of CTCL. Because of that, the terms MF and CTCL are often used interchangeably, and sometimes imprecisely. For example, much of the research on MF reported in the medical journals is listed under the name CTCL, even though MF is just one type of CTCL. This can be a source of confusion. All cases of MF are CTCL, but not all CTCL cases are MF. Mycosis fungoides can appear anywhere on the body but tends to affect areas of the skin protected from sun by clothing.
MF is an indolent type of CTCL, follows a slow, chronic course and very often does not spread beyond the skin. Over time, in about 10% of cases, it can progress to lymph nodes and internal organs. Symptoms of MF can include flat, red, scaly patches, thicker raised lesions calls plaques, and sometimes large nodules called tumors. The disease can progress over many years, often decades.
Although there is continuing research, at this time no single factor has been proven to cause this disease. There is no supportive research indicating that it is genetic or hereditary. Studies have failed to show connections between chemical exposure, environment, pesticides, radiation, allergies and occupations. Exposure to Agent Orange may be a risk factor for developing CTCL for veterans of the Vietnam War, but no direct cause-effect relationship has been established.
While the number of new cases diagnosed each year is relatively low (about 3,000), it is estimated that, since patients have a very long survival, there may be as many as 30,000 patients living with cutaneous lymphoma in the United States and Canada. Due to the difficulty of diagnosing the disease in its early stages and the lack of an accurate reporting system, these numbers are estimates.
One of the challenges in describing this disease is that it doesn’t look the same for all patients. Patches, plaques and tumors are the clinical names for different skin manifestations and are generally defined as “lesions.” Patches are usually flat, often scaly and look like a “rash.” Plaques are thicker, raised lesions. MF patches and plaques are often mistaken for eczema, psoriasis or “non-specific” dermatitis until an exact diagnosis is made.
Tumors are raised “bumps” or “nodules” which may or may not ulcerate (open sores). A common characteristic is itching, although not all patients experience this symptom. Most of the time patients present with patches or plaques. Only rarely are the tumors the presenting lesion. While it is possible to have all three of these types of lesions at the same time, most people who have had the disease for many years experienced only one or two types of lesions, generally patches and plaques.
While on average MF is an indolent, chronic disease, the course in individual patients is unpredictable. It can be slow, rapid or static. Most patients will only experience skin symptoms without serious complications. About 10% will see the disease progress to lymph nodes or other internal organs with serious complications. Unlike other types of skin cancer, chiefly melanoma, MF almost never progresses to lymph nodes and internal organs without showing very obvious signs of progression in the skin. Many patients live normal lives while treating their disease, some remaining in remission for long periods of time.
MF is very difficult to diagnose in early stages as symptoms and skin biopsy findings are similar to other skin conditions, leading to frequent misdiagnosis. Patients may go on for years before a definitive diagnosis is established. Both the clinical findings (based on both history and examination) and the skin biopsy findings are essential for diagnosis. Physicians will examine lymph nodes and often order blood tests including a test for Sézary cells in the blood. Other screening tests such as computed tomography (CT) or positron emission tomography (PET) scans may be indicated, depending on the patient’s history.