The more moles one has the higher the risk that one of them will become cancerous, although the danger is still very small. A 2003 study estimated that the risk for a single mole to develop into melanoma by age 80 is 1 in 3,164 in men and 1 in 10,800 for women. (The risk is higher, however, with atypical moles. One study of people with melanoma indicated that the presence of even one atypical mole doubled the normal risk. Having 10 or more increased the chance 12-fold.) Any mole should be watched for changes, particularly in people with fair skin and other risk factors. However, simply having them should not cause alarm.
Psoriasis and Its Treatments. Psoriasis increases the risk for squamous cell carcinoma, but studies conflict on whether it has any effect on melanoma. One study, in fact, reported a lower risk. Nevertheless, there is some evidence that long-term treatment for psoriasis using UVA radiation (PUVA) may increase the risk for melanoma. In one study, there was a significantly higher risk even with relatively few treatments. In one study, invasive melanoma had occurred in 2.8% of patients 15 or more years after the initial treatment.
Non-Skin Medical Conditions
- Non-Hodgkin's Lymphoma. Survivors of either non-Hodgkin's lymphoma or melanoma face a higher risk for the other malignancy. These may have common causes, such as exposure to UV radiation or shared genetic factors.
- Immunosuppressed Patients. Individuals whose immune systems are suppressed because of certain medications, organ transplantation, or specific medical conditions such as AIDS are also at risk. (Melanoma has also developed in patients who received heart transplants from donors who had the disease.) Immune-suppressing drugs used to treat autoimmune disorders may increase risk. In 2005, the FDA warned of potential skin cancer risks associated with the eczema drugs pimecrolimus (Elidel) and tacrolimus (Protopic).These drugs are ointments that are rubbed on the skin. The FDA recommends that patients limit the amount of ointment they apply, and avoid direct exposure to sunlight. Despite these concerns, the number of skin cancers has not increased, although large numbers of patients have been and continue to be treated with these drugs.
- Rheumatoid arthritis. The rheumatoid arthritis drug etanercept (Enbrel) does not raise the risk for developing squamous cell skin cancer, according to research published in 2005 in the Archives of Dermatology. Researchers analyzed data from more than 1,400 patients who used etanercept for up to 5 years. Etanercept works by blocking tumor necrosis factor (TNF), an immune system chemical messenger that is involved in inflammatory processes and diseases. Previous reports had indicated a possible association between etanercept use and skin cancer risk.
- Endometriosis. Endometriosis may put women with this condition at higher risk for melanoma, although more research is needed to confirm this.
Geographic Location
Australia has the highest melanoma rate in the world. In the US the incidence is highest in California, Florida, and Texas. The disease is by no means limited to such sunny states and countries, however. In general, the risks are highest in regions where the population tends to be blonde and fair-skinned. Norway, for example, has had the highest rate of melanoma in Europe, and rates are soaring in the UK, particularly among men, perhaps because Britons are increasingly vacationing in sunny climates.
Other Forms of Radiation Exposure
Occupational exposure to radiation, such as in health care or industrial settings, may increase the risk for melanoma. Airline pilots, too, are at increased risk for melanoma. It is uncertain, however, whether this higher risk is from excessive exposure to ionizing radiation at high altitudes or because they have more opportunity to spend time in sunny regions. Experts disagree over whether frequent flyers are also at increased jeopardy.
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