What is skin cancer?
Skin cancer occurs when cells in your skin become damaged, often due to excessive sun exposure or tanning bed use. These damaged cells grow faster and cause changes in the appearance of your skin. Although most skin cancers are curable following surgery or other therapies, if not treated, they can spread to other areas of your body.
Treatment strategies and outcomes vary for different types of skin cancer. Most skin cancers are easily treatable when identified early. Routine skin checks and awareness of skin cancer warning signs are key to early detection.
Prevention is also important. The best way to reduce your risk of skin cancer is to minimize sun exposure through the use of sunscreen and sun-protective clothing and to avoid sunburns or the use of indoor tanning beds.
How common is skin cancer?
More people develop skin cancer than any other type of cancer. Approximately one in five people in the U.S. will receive a skin cancer diagnosis before age 70, particularly those with lighter skin tones and a tendency to sunburn.
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Understanding Skin Cancer
Doctors classify skin cancers by the types of skin cells they affect:
- Non-melanoma: Non-melanoma skin cancers are also called keratinocyte carcinomas and include basal cell carcinoma and squamous cell carcinoma. Basal and squamous skin cells are located in the uppermost layers of skin. Although these are the most common skin cancer types, they are less likely to spread than melanoma of the skin.
- Melanoma: Melanoma develops in the skin’s pigment cells (melanocytes). Only about 1% of skin cancers are melanoma, but melanoma is more likely than non-melanoma skin cancer to spread to other areas of the body.
- Merkel cell carcinoma: This rare form of skin cancer starts in Merkel cells—specialized cells located in the top layer of skin that help you feel light touch. Merkel cell carcinoma often grows and spreads quickly.
- Cutaneous lymphoma: This very rare lymphoma starts in infection-fighting white blood cells (lymphocytes) in the skin. There are many types of cutaneous lymphoma that differ widely in how quickly they grow and spread.
The first symptom of skin cancer is typically an unusual change to your skin. Skin cancers vary widely in appearance. Depending on the cancer type and your skin tone, they can be difficult to detect. Skin cancers can also resemble noncancerous skin conditions, such as eczema or psoriasis.
Often, skin cancer develops on sun-exposed areas. However, certain skin cancers, including melanoma, can also appear on sun-protected skin or in hidden places, such as the palms of your hands, soles of your feet, or on the fingernails or toenails.
Signs of skin cancer include:
- Mole that changes size, shape, or color
- Open sore that does not heal
- Pink, red, or brown-colored bump or patch
- Rough, scaly area that may itch and bleed
- Shiny bump or nodule
- Waxy, scar-like area
The ABCDEs of melanoma can help you identify concerning moles or pigmented spots, but identifying an “outlier spot” that’s growing or doesn’t match the rest of your skin spots can also be helpful.
- Asymmetry: Has an irregular shape
- Border: Has uneven edges
- Color: Has color variations
- Diameter: Is larger than a pencil eraser (6 millimeters)
- Evolving: Grows or looks different from other moles or spots
The most common cause of skin cancer is ultraviolet (UV) rays from sunlight or tanning beds. UV rays cause changes (mutations) in a skin cell’s DNA that can lead to cancer formation. People with lighter skin tones who have had a lot of sun exposure, tanning bed use, or multiple sunburns have a higher risk of most types of skin cancer.
Other skin cancer risk factors include:
- Age: Most skin cancers occur in people over age 50. While melanoma occurs after age 60 years on average, it is one of the most common cancers in people under 30 years of age.
- Fair skin: People with lighter skin have different pigment content (melanin) in their skin and so less protection from UV rays, increasing skin cancer risk.
- Family history of skin cancer: You may have a higher risk of skin cancer if a close relative (parent, sibling, or child) in your family has had skin cancer.
- Having many moles: If you have many moles, particularly larger moles, you are more likely to develop melanoma.
- Infections: A common childhood virus, polyomavirus, may be linked to Merkel cell carcinoma. Certain infections are also associated with cutaneous lymphoma.
- Previous skin cancer: Having one skin cancer may make you more likely to develop another one.
- Tanning bed use: According to the American Academy of Dermatology, tanning indoors before age 20 increases your melanoma risk by nearly 50%. And, your risk increases each time you tan.
- Weakened immune system: Your immune system helps fight cancer. Diseases or treatments that weaken your immune system can increase your risk of skin cancer.
When your care team determines your diagnosis, they also assess how advanced the cancer is. This is called its stage. Doctors use TNM staging to indicate how much skin cancer has spread in the body.
Each letter in this system describes an aspect of the cancer:
- Tumor size tells your doctor how large the tumor has grown and how likely it is to have spread.
- Node indicates whether cancer is present in nearby lymph nodes and, if so, how many.
- Metastasis describes whether the cancer has spread beyond the lymph nodes to other parts of the body.
Doctors also determine how serious skin cancer is based on other factors such as the specific type of cancer, location, and how fast it’s growing.
Your doctor will consider all of these factors when making recommendations about your treatment plan. Staging also helps determine your prognosis (likely outcome based on the experience of others).
You can prevent most skin cancers by protecting yourself from UV rays. Avoid indoor tanning beds and when outside:
- Cover up: Wear clothes that cover your skin, a wide-brim hat, and UV-blocking sunglasses.
- Stay in the shade: Find a shady area under an umbrella, tree, or shelter.
- Use sunscreen: Apply sunscreen to exposed skin. Choose a broad-spectrum sunscreen that works to filter UVA and UVB rays with an SPF of 30 or higher. Reapply every two hours and after swimming and exercise.
- Protect children: Pay special attention to children, who may not take steps to protect their skin on their own.
Health care providers recommend monthly self-checks to look for any skin changes that might be an early sign of skin cancer. An annual check by a health care provider is also important.
To perform a self-exam:
- Go to a well-lit room with a mirror. Look at the entire surface of your body.
- Use a hand mirror to check hard-to-see areas and a comb to part your hair so you can see your scalp. You may also ask someone to check the areas you can’t see.
- Note the patterns of freckles, moles, and other skin spots.
- If you find a suspicious change or outlier spot that doesn’t match the rest of your skin spots, let your doctor know.
Diagnostic Tests for Skin Cancer
The first step in care is getting an accurate diagnosis. Your doctor performs a thorough evaluation, which typically includes discussing your medical history, a physical exam, and one or more tests. Tests may include:
A biopsy is a small sample of tissue your doctor collects and sends to a pathologist (lab specialist) for examination under a microscope. Testing biopsied tissue in a laboratory can also provide further information for diagnosis and possible treatments.
There are several kinds of skin biopsies. They may include shaving the top layers of skin (shave biopsy) or using a cylindrical tool to collect deeper layers (punch biopsy). Your doctor may also use a surgical instrument to remove the affected skin (lesion) along with a margin of healthy skin around it (excisional or complete biopsy).
Before the biopsy, you’ll receive an anesthetic injection to numb the area, so you don’t feel pain.
When feasible, your doctor will generally attempt to remove the entire tumor during the biopsy. For some skin cancers, this may complete treatment.
Lymph nodes are small groups of immune cells found all over your body. They are usually the first place skin cancer spreads to. This is particularly true for melanoma and Merkel cell carcinoma. A lymph node biopsy involves collecting cells from these nodes using a fine needle or surgically removing entire nodes.
Your doctor will look for swollen or firm lymph nodes near the tumor through examination or imaging tests. If there are no suspicious nodes and your melanoma is at higher risk for lymph node spread, they may perform a sentinel lymph node biopsy. A sentinel lymph node is the closest node that cancer will most likely spread to. Finding out whether skin cancer has spread to surrounding lymph nodes is important for determining the cancer stage.
Imaging tests can help your doctor find enlarged lymph nodes or distant disease if the cancer has spread to the lymph nodes or others sites of the biopsy. Imaging can also be used to guide a needle biopsy. Types of imaging tests used in skin cancer diagnosis and monitoring treatment include:
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