Everyone is exposed to ultraviolet (UV) radiation from the sun. Small amounts of UV radiation are beneficial to people, and play an essential role in the production of vitamin D. However, overexposure to UV radiation is responsible for two major public health problems: skin cancer and cataract.Emissions from the sun include light, heat and UV radiation. UV radiation reaching the Earth's surface is largely composed of UVA with a small UVB component.
A changing lifestyle and sun-seeking behaviour are responsible for much of the increase in skin cancers. In particular, frequent sun exposure and sunburn in childhood appear to set the stage for high rates of melanoma later in life. Depletion of the ozone layer, which provides a protective filter against UV radiation, may further aggravate the problem.
Skin cancers are divided into nonmelanomas and melanomas.Nonmelanomas (usually basal cell and squamous cell cancers) are the most common cancers of the skin. They are called nonmelanoma because they develop from skin cells other than melanocytes. Because they rarely spread elsewhere in the body, they are less worrisome than melanomas.
Melanoma is a cancer that begins in the melanocytes. Because most of these cells keep on making melanin, melanoma tumors are often brown or black, but this is not always the case. Melanoma most often appears on the trunk of fair-skinned men and on the lower legs of fair-skinned women, but it can appear other places as well. While having dark skin lowers the risk of melanoma, it does not mean that a person with dark skin will never develop melanoma.
Sometimes, clusters of melanocytes and surrounding tissue form noncancerous growths called moles. (Doctors also call a mole a nevus; the plural is nevi.) Moles are very common. Most people have between 10 and 40 moles. Moles may be pink, tan, brown, or a color that is very close to the person’s normal skin tone. People who have dark skin tend to have dark moles. Moles can be flat or raised. They are usually round or oval and smaller than a pencil eraser. They may be present at birth or may appear later on—usually before age 40. They tend to fade away in older people. When moles are surgically removed, they normally do not return.
People previously treated for a melanoma are at high risk of developing another melanoma, but frequent follow-up exams and self-examination can help diagnose second melanomas earlier-improving chances of survival, according to an article in a recent issue of Cancer (2001;91:1520-1524). For patients who have had one melanoma, the risk of developing a second is 10 to 25 times greater than that for patients without a history of melanoma.
In contrast to malignant melanoma, the non-melanoma skin cancers basal and squamous cell carcinoma are not usually fatal but surgical treatment can be painful and result in scars. Non-melanoma skin cancers are most frequent on those parts of the body that are commonly exposed to the sun such as ears, face, neck and forearms. The finding that they are more frequent in outdoor than in indoor workers suggests that the accumulated life-time exposure to UV radiation plays a major role in the development of non-melanoma skin cancers.
Although melanoma accounts for only 4 percent of all dermatologic cancers, it is responsible for 80 percent of deaths from skin cancer; only 14 percent of patients with metastatic melanoma survive for five years.1 The intractability of advanced melanoma shows how much we have to learn about the changes that facilitate the vertical growth and deep invasion of melanoma and about the mechanisms that block the effectiveness of chemotherapy.
The American Cancer Society (ACS) recommends skin exams every three years for adults between ages 20 and 40 and yearly exams after age 40. These screening exams involve a head-to-toe inspection of your skin by someone qualified to diagnose skin cancer, such as a dermatologist or nurse specialist. If you have risk factors for skin cancer — fair skin, a history of severe sunburns, one or more dysplastic moles, or a family history of melanoma — talk to your doctor about more frequent screenings. Sometimes frequent screenings are recommended for all close family members of a person with melanoma.
The ABCDE rule can help you remember what to look for when you're checking any moles on your skin:
A for asymmetry: A mole that, when divided in half, doesn't look the same on both sides
B for border: A mole with edges that are blurry or jagged
C for color: Changes in the color of a mole, including darkening, spread of color, loss of color, or the appearance of multiple colors such as blue, red, white, pink, purple or gray
D for diameter: A mole larger than 1/4 inch in diameter (about the size of a pencil eraser)
E for elevation: A mole that is raised above the skin and has a rough surface.
When it comes to melanoma – the most serious form of skin cancer that accounts for more than 75 percent of skin cancer deaths – knowing the facts about its causes and characteristics could save your life. Dermatologists hope that dispelling some common myths about melanoma could help more people understand their risk factors and be more aware of melanomas that don’t fit the typical diagnostic mold.
“Despite our ongoing public education efforts on the causes and symptoms of melanoma, a number of misconceptions about this potentially deadly disease exist,” said dermatologist Diane R. Baker, MD, FAAD, president of the American Academy of Dermatology (Academy). “These myths could cause some people to think they are not at risk for melanoma because of their skin type or to dismiss warning signs because they are not typical symptoms of the disease.”
Myth: All melanomas follow the ABCD rule.
Fact: When the ABCD rule for early melanoma diagnosis was designed more than 20 years ago, it offered a tool for physicians to aid in distinguishing potentially cancerous lesions from benign pigmented moles. The ABCD acronym stands for Asymmetry (meaning one half of the mole is different from the other), Border Irregularity (the edges or borders of melanomas are usually ragged or notched), Color (melanoma often has a variety of hues and colors within the same lesion), and Diameter (most melanomas are usually greater than 6 mm in diameter when diagnosed, although they can be smaller).
However, like all rules, there are bound to be exceptions. Numerous studies show that not all melanomas follow the ABCD rule. One study published in the May 2003 issue of the Journal of the American Academy of Dermatology (JAAD) examined a specific type of melanoma known as nodular melanoma (NM) that does not fit the ABCD criteria for melanoma diagnosis. NMs commonly occur as symmetric, elevated lesions that are uniform in color and non-pigmented.
“When most people think of melanoma, they often associate a black- or brown-colored lesion or a mole that changes colors,” said Dr. Baker. “This study demonstrates that nodular melanomas lack a change in color, with 71 percent of the NM patients participating in the study reporting no noticeable change in color versus 57 percent of patients classified with the more traditional ‘superficial spreading melanoma’ that noted a color change in their lesions. This is one example where NM patients relied more on the changing nature of their suspicious lesions – primarily bleeding and catching on clothing – than the ABCD characteristics.”
Another study, published in the December 8, 2004, issue of the Journal of the American Medical Association, supports the argument that not all melanomas follow the ABCD rule – noting data which demonstrated the smaller size (less than 6 mm) and the “evolving” nature of some melanomas, including changes in size, shape and symptoms (commonly involving itching, bleeding or tenderness).
Myth: Moles that have hairs are not cancerous.
Fact: Although the vast majority of melanocytic (or pigmented) moles with hairs are benign, a new study published in the March 2007 issue of JAAD references three cases where the presence of one or more hairs in a pigmented lesion proved to be invasive melanoma. The authors of the study stress that a melanoma diagnosis should not be automatically ruled out in cases of pigmented lesions simply because they contain hair, and patients should closely monitor all moles for signs of skin cancer – regardless of whether or not hair is present.
“As the study investigators mention, one possible explanation as to why this myth originated is that when melanoma was commonly diagnosed in more advanced stages many years ago – marked by larger and thicker lesions – it would subsequently destroy the surrounding hair follicles,” noted Dr. Baker. “Today, dermatologists are diagnosing melanomas much earlier, when the lesions are thinner and before hair follicles are wiped out. This study clearly illustrates that melanoma can defy the odds in terms of diagnosis and all suspicious lesions should be evaluated without exception.”
Myth: People of color don’t get skin cancer.
Fact: While Caucasians are 10 times more likely to be diagnosed with melanoma than other races, studies show that African-Americans are more likely to develop the condition on non-sun-exposed areas of the body – such as the nails, soles of the feet, palms of the hands, mouth, nasal passages and genitals. One study showed that while 90 percent of Caucasian patients develop melanoma on skin that is regularly sun-exposed, only 33 percent of African-American patients developed the condition in these areas.
“The common belief that melanoma and other skin cancers don’t affect people of color goes hand-in-hand with the myth that skin cancers only develop in sun-exposed areas,” explained Dr. Baker. “In fact, these ‘hidden’ melanomas are extremely dangerous, because they don’t always follow the ABCD rule for melanoma detection, their symptoms can mimic other medical conditions, and they are not easily detected. People of color, like all patients, need to heed the Academy’s recommendation to conduct regular skin self-examinations and learn how to spot the warning signs of hidden melanomas.”
Experts stress that when diagnosed, melanoma in skin of color patients has often spread to other parts of the body. A study published in the January 2004 issue of JAAD compared the stage of initial melanoma diagnosis of African-American patients versus Caucasian patients and their respective prognoses. Of the 649 patients studied, 32.1 percent of African-American patients were diagnosed with stage III or stage IV melanoma, as compared to only 12.7 percent of Caucasian patients. When melanoma progresses to these advanced stages, it is usually fatal.
“The common thread running through all these myths is that when it comes to melanoma, patients and dermatologists alike need to think outside the box,” added Dr. Baker. “Patients need to be vigilant in monitoring their skin for any changes that could signal a problem, and dermatologists play a pivotal role in diagnosing melanoma at its earliest and most treatable stage.”
It is estimated that 55,100 cases of invasive melanoma will be diagnosed in the United States in 2004 (4% of all cancer cases) and that 7,910 patients will die of the disease (1% to 2% of all cancer deaths). Melanoma is estimated to be the fifth and seventh most common cancers in men and women, respectively, among new cases of cancer in the United States in 2004. For these reasons, physicians,patients ,general people involved in diagnosing and treating cancer will need to know about the staging of this common cancer.One American dies of melanoma almost every hour (every 65 minutes). In 2007, 8,110 deaths will be attributed to melanoma – 5,220 men and 2,890 women. The five-year survival rate for people whose melanoma is detected and treated before it spreads is 99 percent.
One of the most important prognostic features of malignant melanoma is the involvement of regional lymph nodes. The aim of this study is to identify the sentinel lymph node which is the first node to be involved by metastases from malignant melanoma and then decide which patients can benefit from lymph node dissection and which will only need clinical follow-up.
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