Skin Cancer & Moles: Warning Signs, Prevention and Treatment
Skin cancer is the most common cancer, and it is highly treatable when caught early. Here is what to look for, how to lower your risk, and what treatment involves.
Written and medically reviewed by Dr. Danny Guo, MD, FRCPC, FAAD, board-certified dermatologist✓ Reviewed Nov 2026· 2 full videos · 14 Shorts
Key takeaways
- Skin cancer is the most common cancer, and most cases are highly treatable when found early.
- Not every skin cancer is a dark mole. A pink scaly patch, a shiny bump or a sore that won't heal can also be warning signs.
- Use the ABCDEs to check moles, and watch for any spot that looks different from the rest.
- Daily sunscreen, shade and avoiding tanning beds lower your risk.
- Mohs surgery offers the highest cure rates for many skin cancers on the face while saving healthy skin.
What does skin cancer look like?
The three most common skin cancers look quite different. Basal cell carcinoma, the most common, often appears as a shiny, pearly or pink bump, or a sore that bleeds, heals and comes back. Squamous cell carcinoma tends to be a rough, scaly or crusted patch or a firm, tender bump on sun-exposed skin. Melanoma, the most serious, usually appears as a new or changing mole or dark spot.
For moles, use the ABCDEs: Asymmetry, uneven Borders, more than one Colour, a Diameter larger than a pencil eraser (about 6 mm), and Evolving, meaning any change in size, shape or colour. A spot that looks different from your other moles, sometimes called the 'ugly duckling' sign, is also worth checking.
Some spots that look worrying are harmless, such as seborrheic keratoses and cherry angiomas, and some harmless-looking spots are not. If you are unsure, have it checked.
Full video · 14 min
Skin Cancer Doesn't Look Like You Think
How can you lower your risk of skin cancer?
Ultraviolet exposure is the main cause of most skin cancers, and the damage adds up over a lifetime. Use a broad-spectrum sunscreen of SPF 30 or higher every day, seek shade during the strongest sun, and wear a hat, sunglasses and protective clothing. Avoid tanning beds completely.
Your risk is higher if you have fair skin, many moles, a history of blistering sunburns, a personal or family history of skin cancer, or a weakened immune system. People with darker skin can still get skin cancer, often on the palms, soles and nails, where it is easily missed.
Check your skin once a month, including your scalp, back, palms, soles and between your toes, and see a dermatologist for anything new or changing.
How is skin cancer treated?
Most skin cancers are treated with a minor procedure in the clinic under local anaesthetic. The right option depends on the type of cancer, its size, its location and your health.
Mohs surgery removes the cancer in thin layers and checks all of the edges under the microscope while you wait, taking more tissue only where cancer remains. It offers the highest cure rates for many basal and squamous cell carcinomas while saving as much healthy skin as possible, which is why it is often used on the face, ears, hands and other sensitive areas.
Scars are usually longer than the spot itself, because skin has to be closed in a line that lies flat and heals well. Some early or superficial skin cancers can be treated without surgery, using prescription creams, freezing or light-based treatment.
Full video · 12 min
10,000 Skin Cancer Surgeries Later: 5 Things Everyone Should Know
What's new in skin cancer research?
Treatment for advanced skin cancer has changed dramatically in the last decade. Immunotherapy and targeted therapies have improved survival for many people with melanoma and other skin cancers, and personalized melanoma vaccines are being studied in clinical trials.
For most people, the most powerful tools are still prevention and early detection. Ask your dermatologist which new options apply to your situation.
Quick answers · 2 Shorts
Frequently asked questions
How often should I get a skin check?
Most people benefit from checking their own skin once a month. People at higher risk, such as those with many moles, a history of skin cancer or a strong family history, usually need regular professional skin checks, often once a year or more. Ask your dermatologist what is right for you.
What are the ABCDEs of melanoma?
Asymmetry (one half does not match the other), Border (irregular or blurred edges), Colour (more than one colour), Diameter (larger than about 6 mm, though melanomas can be smaller) and Evolving (any change in size, shape, colour or symptoms such as bleeding or itching).
Is skin cancer curable?
Most skin cancers are curable, especially when they are found and treated early. Basal and squamous cell carcinomas have very high cure rates. Melanoma is also highly treatable when caught early, which is why checking your skin matters.
What is Mohs surgery?
Mohs surgery is a specialized technique for removing skin cancer in stages. After each thin layer is removed, its edges are checked under the microscope while you wait, and more tissue is taken only where cancer remains. It has the highest cure rates for many skin cancers and saves healthy skin.
Can people with darker skin get skin cancer?
Yes. Skin cancer is less common in darker skin but is often diagnosed later, when it is harder to treat. In darker skin, melanoma often appears on the palms, soles, under the nails or inside the mouth, so these areas are worth checking.
When to see a dermatologist
See a dermatologist promptly for any spot that is new, changing, bleeding, itchy or not healing, or that looks different from your other moles. Early diagnosis makes treatment simpler and more successful.
In Calgary?
Dr. Guo sees patients at Rejuvenation Dermatology. Learn more at calgaryderm.com.
Sources
Educational content only. It is not medical advice and does not replace an assessment by your own doctor or dermatologist.
