Spending time in the sun without protection increases the risk of melanoma, but the potentially deadly skin cancer can occur even on sites with minimal sun exposure, doctors warn.
Melanoma accounts for only about 1% of skin cancers but causes the majority of skin cancer deaths.
Writing in the medical journal CMAJ, two dermatology experts highlight important things to know about the most dangerous form of skin cancer.
“Melanomas can occur anywhere on the body, not only in areas that get a lot of sun,” Dr. Kucy Pon told Reuters Health by email. She said the most common site in men is the back, while for women it is the leg.
More than 90% of melanomas with the most common genetic characteristics are caused by too much ultraviolet radiation, either from the sun or from sun lamps like the kind used at tanning salons, Pon and co-author Robert Micieli say.
But for some melanomas on peripheral body parts like palms and soles, and on mucosal surfaces, sun exposure is not the primary cause, the authors note. In these cases, the cancer’s development may more closely match the chain of events that lead to non-skin-cancers.
Pon said the incidence of melanoma has been rising over the last 30 years, with an estimated 192,300 new cases expected in the U.S. in 2019.
The disease can affect anyone, regardless of skin color, Pon said.
Along with sun exposure, risk factors include advancing age, moles, many atypical looking moles and a family history of melanoma.
“The first sign of a melanoma is an unusual looking mole or freckle, said Pon, a dermatologist at Sunnybrook Health Sciences Center in Toronto.
But she and Micieli warn that in one of every 10 melanoma patients, the lesion may have no color at all and is difficult to diagnose.
“These unpigmented melanomas may be pinkish-looking, reddish, purple, normal skin color or essentially clear and colorless,” said Dr. Ronald Moy, a board-certified dermatologist in Beverly Hills, California and a spokesperson for the Skin Cancer Foundation.
Moy said in an email that these atypical melanomas can resemble other forms of skin cancers or, worse, may be mistaken for benign moles, scars or cysts, which may prove dangerous, since early detection of melanoma is critical.
Indeed, Pon and Micieli say any lesions suspected of being melanoma should be examined by a dermatologist, especially a lesion with so-called “ABCDE” features: Asymmetry, Border irregularity, Color variation, Diameter over 6 mm and Evolving or changing.
“Prevention and early detection are key,” agreed Dr. Emily Newsom, a dermatologist at UCLA Health in Los Angeles.
For prevention, dermatologists recommend frequent reapplication of at least 30 SPF broad-spectrum sunscreen as well as sun protective clothing and wide brimmed hats.
Finally, Pon and Micieli advise, when patients do have melanoma – particularly in cosmetically sensitive areas like face – the optimal way to excise it is with Mohs surgery, in which thin layers of the tumor are removed until only cancer-free tissue remains.
Researchers have made “tremendous breakthroughs” in learning about the genes involved in melanoma, said Dr. Jeffrey Farma, co-director of the Melanoma and Skin Cancer Program at Fox Chase Cancer Center in Philadelphia.
As a result, Farma added, great strides are being made in targeted therapies and immunotherapies for treating advanced melanoma and improving survival.