Sun spots, also known as solar lentigines or liver spots, are flat, brown or black spots that appear on areas of skin exposed to the sun. While sun spots themselves are harmless, they can sometimes develop into skin cancer or be a sign of existing skin cancer.
What causes sun spots?
Sun spots are caused by exposure to ultraviolet (UV) radiation from the sun or tanning beds. They form when melanin, the pigment that gives skin its color, grows in clusters instead of being spread evenly across the skin’s surface. Anyone can develop sun spots, but they are more common in people over age 40 and those who spend a lot of time in the sun.
Are all sun spots cancerous?
The vast majority of sun spots are benign and do not turn into skin cancer. However, in some cases, sun spots may be precancerous or early stage skin cancers:
- Actinic keratosis – Precancerous rough, scaly patches on the skin caused by years of sun exposure. Left untreated, some may turn into squamous cell carcinoma.
- Lentigo maligna – An early form of melanoma confined to the outermost layer of skin. Begins as a sun spot with irregular borders and colors.
- Squamous cell carcinoma – The second most common type of skin cancer. Can begin as scaly red patches or open sores.
So while most sun spots are harmless, it’s important to monitor them for any changes in size, shape, or color, as this could indicate cancer development.
What do cancerous sun spots look like?
Cancerous sun spots may have some distinct characteristics that set them apart from regular benign sun spots:
- Irregular shape: Benign sun spots tend to have smooth, round, or oval shapes with defined borders. Cancerous spots have uneven, jagged, or blurred borders.
- Irregular coloring: Benign spots are uniformly light brown. Cancerous spots may have tan, brown, black, and even pink or red coloring due to broken blood vessels.
- Larger size: Cancerous spots are often larger than benign spots, which are usually less than 3 mm wide.
- Elevation or depression: Benign spots are flat against the skin. Cancerous spots may be raised above the skin or sunken pitted areas.
- Oozing or crusting: Pre-cancerous and cancerous spots may ooze fluid or blood or develop a crusty surface.
- Itching or pain: Benign spots are not painful. Cancerous spots may itch, burn, or become tender to the touch.
How can you tell if a sun spot is cancerous?
It can be difficult to distinguish between benign and cancerous sun spots just by visual examination alone. The ABCDE guidelines can help identify suspicious spots:
- Asymmetry: One half is unlike the other half in size or shape.
- Border: The spot has an irregular, blurry, or jagged border.
- Color: The color is not uniform and may have shades of tan, brown, black, or red.
- Diameter: The spot is larger than 6mm across, about the size of a pencil eraser.
- Evolving: The spot is changing in size, shape, or color over time.
Here is a table summarizing the differences between benign and cancerous sun spots:
| Characteristic | Benign Sun Spot | Cancerous Sun Spot |
|---|---|---|
| Shape | Round, oval, smooth borders | Irregular, uneven, jagged borders |
| Color | Uniform light brown | Tan, brown, black, pink, red, uneven coloring |
| Size | Usually less than 3mm | Often larger than 6mm |
| Elevation | Flat | Raised or sunken |
| Surface | Smooth | Oozing, crusting, scaly |
| Sensation | None | Itching, burning, tenderness |
| Changes | Stable | Changing size, shape, color |
If you notice any sun spots on your body with the ABCDE features or characteristics of the “cancerous” column in the table, it’s important to get it looked at by a dermatologist right away. They can perform a biopsy if needed to determine if the spot is cancerous.
Where do cancerous sun spots usually appear?
Cancerous sun spots most often develop on areas of the body that receive the most sun exposure. The most common locations are:
- Face
- Ears
- Scalp
- Neck
- Shoulders
- Upper back
- Forearms
- Backs of hands
However, cancerous spots can also show up in areas that don’t see much sun, such as the genitals, buttocks, and eyelids. It’s important to check your entire body for any suspicious spots.
Who is most at risk for cancerous sun spots?
While anyone can develop skin cancer, some people are at higher risk due to their genetics or amount of sun exposure over a lifetime. Risk factors include:
- Light skin tone
- Blonde or red hair
- Blue or green eyes
- History of severe sunburns
- Personal or family history of skin cancer
- Living closer to the equator or at a high altitude
- Outdoor hobbies or occupation
- Tanning bed use
- Weaker immune system due to medical condition or medication
People at high risk should take extra precautions against sun exposure and be vigilant about monitoring existing sun spots or any new spots that develop.
How can sun spots turn into skin cancer?
There are a few ways sun spots can transform into skin cancer over time:
- Actinic keratosis: Years of UV damage causes precancerous lesions that may advance to squamous cell carcinoma.
- Lentigo maligna: UV radiation triggers abnormal melanocyte growth, forming an early stage melanoma in situ.
- DNA damage: UV alters skin cell DNA, leading to uncontrolled growth and potential tumor formation.
- Weakened immunity: Sun exposure reduces the skin’s immune function, allowing abnormal cells to multiply.
In most cases, these changes happen gradually over many years. Often a sun spot will slowly grow in size, become irregularly shaped, change colors, or develop a rough surface before it becomes fully cancerous. That’s why monitoring sun spots and having them examined regularly can help catch skin cancers early when they are most treatable.
Can sun spots turn into melanoma?
Yes, sun spots definitely have the potential to develop into melanoma, the most dangerous form of skin cancer. Here is how it can happen:
- UV radiation from the sun or tanning beds causes damage to melanocytes, the cells that produce melanin.
- With further UV exposure over time, these damaged melanocytes grow out of control and cluster together, forming a sun spot.
- The abnormal melanocytes continue multiplying within the sun spot into a lesion called lentigo maligna.
- Over months or years, the lentigo maligna can penetrate deeper into the layers of the skin, becoming an invasive melanoma.
Melanoma accounts for only about 1% of skin cancer cases but a majority of skin cancer deaths. When caught early, the 5-year survival rate for melanoma is 99%. But that drops to just 25% when it spreads to distant areas of the body.
That’s why it’s so important to identify melanoma in its earliest stages when it first appears as an irregular sun spot. If you notice any spots getting bigger, changing shape or color, or meeting the ABCDE guidelines, get screened right away.
Can you prevent sun spots from turning cancerous?
The best way to prevent sun spots from becoming skin cancer is to limit your UV exposure from the start. Steps you can take include:
- Apply broad-spectrum SPF 30+ sunscreen daily.
- Wear protective clothing like hats and long sleeves outside.
- Avoid being outdoors during peak sun hours (10am-2pm).
- Don’t use indoor tanning beds.
- Examine your skin monthly and note any new spots or changes in existing spots.
- See a dermatologist annually for a full body skin cancer screening.
- Have any suspicious spots biopsied and removed early.
It’s also important not to pick at or irritate existing sun spots, as that can cause further skin damage and potential cell mutations.
Can sun spots be removed?
If you have sun spots that are cosmetically bothersome or showing signs of possible skin cancer, there are effective removal options:
- Cryosurgery: Freezing off spots using super cold liquid nitrogen.
- Laser therapy: Using focused light beams to destroy spots.
- Dermabrasion: Sanding down spots with a rotating instrument.
- Chemical peels: Applying acid solution to peel away top skin layers.
- Excision: Cutting out spots surgically.
Your dermatologist can determine the best treatment method for your particular spots. In some cases, they may take a biopsy first to check for cancer before removing them.
When to see a doctor
You should make an appointment with your dermatologist if you notice any of the following with your sun spots:
- ABCDE criteria of melanoma
- Bleeding, oozing, or crusting
- Itching or pain
- Rapid growth or changes in shape/color
- Appearance of many new spots
Your dermatologist can examine any suspicious spots and determine if biopsy or removal is recommended. Catching developing skin cancer early is crucial for effective treatment.
Takeaways
- While most sun spots are benign, some may potentially turn into skin cancer over time with continued sun exposure.
- Irregular shape, uneven color, larger size, and changing over time are red flags for cancerous spots.
- Sun spots that become melanoma go through gradual changes starting as harmless looking growths.
- Limiting your UV exposure, monitoring spots regularly, and getting annual skin checks are important to stop spots from becoming cancer.
- Suspicious looking sun spots should be examined promptly by a dermatologist to determine if biopsy or removal is required.