The most serious type of skin cancer, melanoma develops in the cells that produce melanin (melanocytes) that give skin its color. Exposure to ultraviolet radiation from sunlight or tanning lamps and beds increases the risk of developing melanoma. Melanomas can develop anywhere on the body but most often develop in areas that have been exposed to sun.
The following departments see patients with melanoma:
What Is Melanoma?
Melanoma is a type of skin cancer caused by the cancerous growth of pigment producing cells in the skin called melanocytes.
The body’s largest organ is the skin. It performs several functions. It covers and protects the organs inside the body from heat, injury, germs, infections, and damage caused by ultraviolet (UV) radiation. It also stores water and fat, helps control body temperature, and produces vitamin D.
The skin consists of three layers: the epidermis, the dermis, and the subcutis.
The epidermis is the thin top layer of the skin. It consists mostly of flat cells called squamous cells. Round cells called basal cells are found below the squamous cells. Melanocytes are found among the basal cells in the deepest part of the epidermis. Exposure to UV radiation causes melanocytes to produce more of the brown pigment melanin, which causes the skin to darken (tan).
The dermis is the middle layer of the skin. It is much thicker than the epidermis and contains hair shafts, blood vessels, lymph vessels, glands, and nerves. Some glands produce sweat, which helps keep the body cool. Other glands produce an oily substance called sebum, which helps prevent the skin from drying out. Tiny openings in the skin called pores allow sweat and sebum to pass through the surface of the skin.
The subcutis is the deepest layer of skin. It contains proteins and fats, which help the body retain heat. It also functions as a shock absorber to keep the body’s organs safe.
There are several kinds of benign (noncancerous) growths of the skin. These include moles (melanocytic nevi), seborrheic keratoses, hemangiomas, lipomas, and warts. Benign growths are typically not life threatening. They can usually be removed and don’t tend to regrow. They don’t invade surrounding organs or tissues, nor do they spread to distant sites around the body.
Malignant growths (such as melanoma, basal cell cancer, or squamous cell cancer) may be life threatening. They can usually be removed but sometimes regrow. These growths may invade and damage nearby organs or tissues and may spread to distant sites around the body.
Melanoma begins in the melanocytes. The disease can occur on any surface of the skin, including, in rarer cases, the hands and feet (acral sites); mucosal (wet) sites, such as the mouth or genital area; and within the eye. In men, it is commonly found on the head, neck, or between the shoulders and hips. In women, it is commonly found on the lower legs or between the shoulders and hips.
The disease is rare in people with dark skin, but when it does develop, it is often found in acral areas, such as under the fingernails or toenails, or at mucosal sites.
Melanoma is less common, but far more dangerous, than other skin cancers. It accounts for only a small percentage of skin cancers but causes the most deaths of any skin cancer type.
According to the American Cancer Society, melanoma is on the rise in the United States, with the number of new cases increasing for the past 30 years (American Cancer Society 2015).
Melanoma is prevalent among the young. It is the most common form of cancer in the 25-29 year age group and the second most common form of cancer in the 15-29 year age group.
It is more likely than other skin cancers to spread (metastasize) to other parts of the body.
Symptoms of Melanoma
Melanomas may arise from preexisting moles, but they more commonly originate within normal looking skin.
A change in the color, shape, or size of an existing mole is many times the first symptom of melanoma. The ABCDE rule can help determine if a mole is suspicious and should be checked by a physician.
ABCDE stands for the following:
Asymmetry
The shape of one half of a mole is different from the other half.
Border
If a mole has edges that are irregular, blurred, notched, or ragged, or it has a border that is not clearly defined, it may be cancerous.
Color
Color that is uneven may be a sign a mole is cancerous. Shades of black, brown, or tan may be present in the mole, as well as areas of white, gray, pink, or blue.
Diameter
A change in the size (usually an increase) of a mole may be cause for concern. Melanomas can be small but are generally larger than the size of a pea (bigger than 6 millimeters or about a ¼ inch).
Evolving
If a mole has changed over the course of a couple of weeks or months, have it looked at by a physician.
(American Cancer Society 2015)
Melanomas vary in appearance. Some melanomas may have more abnormal features than others. Not all of the features named in the ABCDE rule need to be abnormal for a mole to be cancerous.
The texture of a mole may also change. This generally happens in the more advanced stages of melanoma. The skin on the surface of the mole may look broken down or scraped. It may feel hard or lumpy and ooze or bleed. Melanomas may be itchy, painful, or tender.
Causes of Melanoma
Although the exact causes of melanoma remain unknown certain risk factors—things that increase an individual's chances of developing a cancer—have been identified. While risk factors may be useful in identifying high-risk individuals, they do not determine whether a person develops a disease. Some risk factors, such as sun exposure, are within a person’s control, while others, such as age, are not.
Possible risk factors for any type of skin cancer include
- Exposure to ultraviolet (UV) radiation: Too much exposure to ultraviolet (UV) radiation is a major risk factor for skin cancer. The most common source of UV radiation is sunlight. UV radiation from the sun’s rays can damage the skin and cause cancer. Severe sunburns (in both childhood and adulthood), lifetime sun exposure, and tanning all affect a person’s chance of developing skin cancer. Sand, pavement, water, snow, and ice all reflect the sun’s rays. The sun’s rays can penetrate clouds, light clothing, windows, and windshields.
- Sunlamps and tanning booths: Sunlamps, tanning booths, and other sources of artificial radiation are just as dangerous as natural sources. People under age 30 who use sunlamps and tanning booths are at an even greater risk of developing skin cancer, melanoma included.
- Personal history: People who have had melanoma in the past are at an increased risk of developing it again in the future. People who have had basal cell or squamous cell cancer in the past are at an increased risk of developing another skin cancer of any kind.
- Family history: People with two or more close family members who have or have had skin cancer are at increased risk of developing the disease.
- Having certain physical traits: Having certain physical traits, such as pale skin, red or blond hair, light-colored eyes (blue, green, gray), or freckles, increases a person’s risk of developing skin cancer.
- Certain medical conditions or medications: Having certain medical conditions or taking certain medications (such as some antibiotics, hormones, or antidepressants) can increase the skin’s sensitivity to the sun, thereby increasing the risk of developing skin cancer. Having a weak immune system or taking medications that stop the immune system from working to its full potential also increase a person’s risk.
- Gender: In the United States, skin cancer is more common in men than in women. However, this statistic varies with age. The risk is higher for women under age 45 and for men above age 45. (American Cancer Society 2015)
Possible risk factors specific to melanoma include
- Age: A person’s risk of developing melanoma increases with age. However, it is also one of the most common cancers found in people under 30 years old.
- Moles: A common mole is round or oval shaped with a smooth, evenly-colored (pink, tan, brown) surface and is usually smaller than the size of a pea. The risk of developing melanoma increases with the number of common moles an individual has. Individuals with more than 50 moles are at increased risk of developing melanoma.
- Atypical nevus: An atypical nevus is an unusual looking benign mole that may have some features resembling a melanoma. People with multiple atypical nevi are at increased risk of developing melanoma.
- Xeroderma pigmentosum (XP): Xeroderma pigmentosum (XP) is a rare genetic disorder that inhibits a person’s ability to repair damage caused by sunlight. People with XP have a greater risk of developing melanoma and other skin cancers at a young age.
Stages of Melanoma
Staging is the process of determining how widespread or advanced the cancer is. It is an important part of diagnosis because it is used to determine the most appropriate treatment options for patients and provide them with a prognosis.
The stage of melanoma is based on several factors, including how deeply it has penetrated the skin, whether it has ulcerated (broken open), and whether the cancer cells have spread to nearby lymph nodes or other organs.
To determine the stage of the disease, physicians need to remove the entire melanoma. The regional lymph nodes are assessed by a clinical exam, and a sentinel lymph node biopsy is advised for melanomas that have certain microscopic characteristics that take into account their depth, whether they are ulcerated or not, and how rapidly they are proliferating. A fine needle aspiration biopsy may be performed instead if the regional lymph nodes are enlarged on the clinical exam. The physician may also perform a series of blood and imaging tests based on the results of these tests.
The clinical stage of melanoma is based on the findings of the physical exam, skin biopsy, lymph node biopsy, and any imaging or blood tests that are performed.
Stage 0
Cancer is present in the top layer of skin (epidermis only). This stage is also referred to as melanoma in situ.
Stage I - II
The melanoma is localized to the skin with no evidence of spread to the lymph nodes or other organs. Stage II melanomas have more adverse features compared to Stage I melanomas.
Stage III
The melanoma has spread to the regional lymph nodes.
Stage IV
The melanoma has spread to distant organs, such as the lungs, liver, or brain.
For more detailed information on stages of melanoma, visit the staging section of the American Cancer Society’s melanoma website.
References
American Cancer Society. 2015. Overview Guide: Melanoma Skin Cancer Overview.
National Cancer Institute. 2010. What You Need To Know About™ Melanoma and Other Skin Cancers. PDF. Bethesda: National Cancer Institute, National Institutes of Health, U.S. Department of Health and Human Services.
Patient Resource, LLC. 2014. Patient Resource Cancer Guide: Understanding Cancer Immunotherapy. Overland Park: PRP Patient Resource Publishing.