The question of whether a common “sunspot” can turn into cancer is a major concern for many people with a history of sun exposure. While most spots that appear after sun exposure are harmless, a specific type of sun-induced lesion is considered precancerous and can progress to skin cancer. Understanding the differences between these skin growths is important for managing skin health and knowing when to seek medical evaluation.
What People Mean When They Say Sunspot
The public uses the term “sunspot” to describe several distinct skin changes, most of which are benign. The most common benign spots are Solar Lentigines, often called age spots or liver spots. These flat, brown patches appear on sun-exposed areas like the face and hands and are simply areas of concentrated pigment caused by chronic ultraviolet (UV) exposure. They are purely a cosmetic issue and have no potential to become cancerous.
Another frequent benign growth is the Seborrheic Keratosis. This lesion often appears waxy, raised, or “stuck-on,” ranging in color from tan to dark brown. Seborrheic keratoses are harmless and do not transform into skin cancer, though they may become irritated. The skin lesion that carries true risk is the Actinic Keratosis (AK), which is the actual precancerous spot that can progress to malignancy.
Understanding Precancerous Skin Lesions
Actinic Keratosis (AK), sometimes called solar keratosis, is the direct result of cumulative UV damage to the skin cells over time. AKs typically present as dry, rough, or scaly patches that may be flesh-colored, pink, red, or brown, and often feel like sandpaper to the touch. These lesions are considered a form of localized, early-stage skin cancer, or carcinoma in situ, because they show abnormal growth patterns in the outermost layer of the skin.
Actinic Keratoses are significant because they can lead to invasive Squamous Cell Carcinoma (SCC), the second most common form of skin cancer. While the majority of AKs remain stable, a small percentage will progress to SCC. Approximately 60% to 80% of all SCC cases are believed to originate from a pre-existing AK.
Because it is impossible to predict which specific AK lesion will become invasive, dermatologists recommend treatment to manage the overall risk. Common treatment options include cryotherapy (freezing the lesion), topical chemotherapy creams, or photodynamic therapy. These treatments destroy the damaged cells, reducing the risk of malignant transformation and preventing the need for more invasive procedures if SCC develops.
Recognizing Dangerous Skin Changes
Learning to recognize specific changes in any skin lesion is important for the early detection of skin cancer, including Squamous Cell Carcinoma (SCC) and Melanoma. For Melanoma, the ABCDE method provides a framework for self-examination.
The letters stand for:
- Asymmetry, where one half of the spot does not match the other.
- Border, referring to edges that are irregular, notched, or blurred.
- Color variation, meaning the lesion contains multiple shades of tan, brown, black, white, red, or blue.
- Diameter, which is a concern if the spot is larger than six millimeters (the size of a pencil eraser).
- Evolving, signifying any change in size, shape, color, or elevation, or the development of new symptoms like bleeding, itching, or crusting.
Signs of potential progression to an invasive SCC, which often arise from an AK, include a persistent open sore that does not heal, rapid growth of the lesion, or the development of tenderness, pain, or bleeding. Because early detection leads to highly successful treatment outcomes, individuals with a history of sun damage, especially those with AKs, should schedule regular full-body skin checks with a dermatologist.
Strategies for Skin Protection
The formation of precancerous and cancerous lesions is driven by accumulated UV radiation, making sun protection the most effective strategy for prevention. Daily use of a broad-spectrum sunscreen that protects against both UVA and UVB rays is recommended. The sunscreen should have a Sun Protection Factor (SPF) of at least 30, applied generously to all exposed skin thirty minutes before going outdoors.
Reapplication is important, typically needed every two hours, or immediately after swimming or heavy sweating. Behavioral changes also reduce risk, such as seeking shade and limiting time outdoors during peak UV hours (generally between 10 a.m. and 4 p.m.). Wearing protective clothing, including wide-brimmed hats and tightly woven fabrics with an Ultraviolet Protection Factor (UPF) rating, provides an additional barrier against damaging rays.
While the sun is a source of Vitamin D, obtaining this nutrient through diet or oral supplements is a safer alternative than relying on unprotected sun exposure. Shielding the skin from UV radiation helps prevent the formation of new lesions and minimizes the risk of existing spots progressing to cancer.