Learn About Skin Cancer Warning Signs

Understanding Skin Cancer Types and How They Develop

Skin cancer occurs when cells in the skin grow abnormally. The three main types are basal cell carcinoma, squamous cell carcinoma, and melanoma. According to the American Academy of Dermatology, more than 5.4 million cases of skin cancer are diagnosed in the United States each year, making it the most common cancer in the country.

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Basal cell carcinoma starts in the basal cells, which are the round cells in the lower layer of the epidermis. This type accounts for about 80 percent of all skin cancers and grows slowly. Squamous cell carcinoma begins in the flat, scale-like cells in the outer layer of skin and represents approximately 20 percent of skin cancers. Both of these types are often called non-melanoma skin cancers.

Melanoma is the most serious type of skin cancer because it can spread to other parts of the body if not caught early. It develops in melanocytes, the cells that produce melanin, which gives skin its color. Melanoma represents about 1 percent of all skin cancers but accounts for the majority of skin cancer deaths. The five-year survival rate for melanoma is about 92 percent when detected early, but drops significantly if it spreads.

Skin cancer develops when DNA in skin cells is damaged, usually by ultraviolet (UV) radiation from the sun or tanning beds. This damage causes mutations that make cells grow out of control. Most skin cancers take years or decades to develop, though some people are at higher risk due to genetics or other factors. Understanding how these cancers form helps explain why recognizing early warning signs matters so much.

Practical takeaway: Learning the three main types of skin cancer—basal cell, squamous cell, and melanoma—helps you understand the differences in how serious they are and why early detection is important for treatment outcomes.

Common Warning Signs You Should Monitor

The most important warning sign for skin cancer is any change in your skin. This includes new growths, changes in existing moles or spots, or anything that looks or feels different. The American Cancer Society recommends examining your skin regularly for these changes. Changes can be subtle, so paying attention to your skin over time helps you notice what's normal for you versus what's new.

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Basal cell carcinoma often appears as a small, shiny bump that may be flesh-colored, brown, or reddish. It sometimes has a rolled edge with a depression or ulcer in the center. These growths may bleed, ooze, or crust over, then heal and repeat the cycle. They typically appear on sun-exposed areas like the face, ears, neck, or hands. Some basal cell carcinomas look like flat, scaly patches that are tan or red and may feel slightly raised.

Squamous cell carcinoma usually appears as a thick, red, scaly bump or patch. It may feel tender or painful. These growths often develop on sun-exposed areas and may have a crusty or ulcerated appearance. Unlike basal cell carcinoma, squamous cell carcinoma can grow more quickly. Some people notice it as a sore that doesn't heal within a few weeks.

Melanoma warning signs follow the ABCDE rule: Asymmetry (one half doesn't match the other), Border irregularity (edges are uneven or notched), Color variation (multiple colors within one spot), Diameter (larger than a pencil eraser, typically 6mm or larger), and Evolution (changing in size, shape, or color). Melanomas can appear anywhere on the body, including areas not exposed to the sun. They may appear as a new spot or as changes in an existing mole.

Other warning signs include sores that don't heal within three weeks, itching or bleeding from a mole or spot, and skin growths that spread beyond their original area. Some people experience pain or tenderness in an area, though skin cancer isn't always painful. A spot that feels different from surrounding skin, such as being harder or more raised, may also warrant attention.

Practical takeaway: Remember the ABCDE rule for melanoma and watch for any sore that doesn't heal, unusual growths, or changes in existing moles. Keeping track of these signs over time helps you notice what's truly different.

Risk Factors That Increase Your Chances

Understanding your risk factors helps you decide how carefully to monitor your skin and how often to have professional skin checks. Risk factors don't mean you will definitely develop skin cancer, but they indicate you may want to be more vigilant about skin surveillance and sun protection.

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Sun exposure is the primary risk factor for all types of skin cancer. The UV rays in sunlight damage DNA in skin cells. Cumulative sun exposure over a lifetime increases risk, as does intense, intermittent exposure that causes sunburns. People who work outdoors, spend significant time at the beach, or live in sunny climates have higher exposure. Research shows that even one severe sunburn, especially in childhood or adolescence, increases melanoma risk later in life.

Family history and genetics play a significant role. People with a family history of melanoma have a much higher risk of developing it themselves. Certain genetic mutations, such as changes in the CDKN2A gene, are associated with familial melanoma. Additionally, people with certain skin types are at higher risk. Those with fair or pale skin, light-colored hair, and light-colored eyes have less protective melanin and burn more easily. People with red or blonde hair have particularly high melanoma risk.

The number and appearance of moles matters. People with many moles, particularly atypical or dysplastic moles that look irregular, have higher skin cancer risk. Atypical moles are often larger than normal moles, have irregular borders, and contain multiple colors. Having 50 or more ordinary moles or any atypical moles increases risk significantly.

Age and previous skin cancer history also factor in. While skin cancer can develop at any age, most non-melanoma skin cancers occur in people over 50. However, melanoma is increasingly common in younger people. Anyone who has had one skin cancer is at higher risk for developing another. Immunosuppression, whether from medical conditions like HIV or from immunosuppressive medications after organ transplants, increases risk substantially. Certain occupational exposures, such as to arsenic or radiation, also increase risk.

Practical takeaway: Identify which risk factors apply to you—whether that's fair skin, sun exposure history, family history, or numerous moles. This information helps you understand why regular skin self-checks and professional examinations are important for your individual situation.

How to Perform Regular Self-Examinations

Regular skin self-examinations allow you to become familiar with your skin and notice changes early. The American Academy of Dermatology recommends examining your entire body once a month, from head to toe. Choose a consistent time each month to make it a habit. You'll need a mirror, and a handheld mirror helps examine harder-to-see areas like your back.

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Start with your face, ears, and scalp. Use the handheld mirror to check your scalp and behind your ears carefully, moving through your hair with your fingers. Look at your lips, gums, and inside your mouth. Continue to your neck, chest, and torso. Women should lift breasts to check underneath. Examine the tops and undersides of your arms and hands, including between fingers and under fingernails.

Check your back using two mirrors or by taking a photo with your phone camera. Examine your buttocks and the backs of your legs. Look at the fronts of your legs, thighs, and shins. Check your feet, including the soles, heels, and between toes. This step is important because melanoma often appears in places people forget to check, like the feet. Pay special attention to any areas that have been sunburned previously.

As you examine, use the ABCDE rule to evaluate any moles or spots. Also look for new growths, changes in size or color of existing spots, or any sores that aren't healing. Note the location and appearance of moles you already have, so you'll recognize if they change. Taking photos of moles with a date helps you track changes over time, especially if you have many moles.

Don't just look—feel your skin too. Run your hands over areas to check for bumps, hard