The term “sunspot” is commonly used to describe any dark mark on the skin that develops after spending time in the sun, but in dermatology, this term usually refers to a specific, benign lesion. These true sunspots, known medically as solar lentigines, are overwhelmingly flat patches of discoloration. The confusion about whether a “sunspot” is raised often stems from the fact that several other, more concerning skin growths frequently appear on sun-exposed skin and are mistakenly grouped under the same casual name. Understanding the differences between these various spots is paramount for proper skin health monitoring.
Defining Solar Lentigines (True Sunspots)
Solar lentigines are small, harmless patches of skin discoloration that result from years of cumulative ultraviolet (UV) radiation exposure. These are sometimes referred to as age spots or liver spots, although they have no connection to the liver’s function. The spots develop because UV radiation triggers a localized increase in pigment-producing cells, called melanocytes, and an accumulation of melanin within the skin’s outer layer.
These lesions appear as clearly defined, flat patches, which can range in color from light tan to dark brown or black. If you run your finger over a true solar lentigo, it feels smooth and level with the surrounding skin. Solar lentigines are most often found on areas that receive the most sun exposure, such as the face, the backs of the hands, the shoulders, and the upper back.
Raised Lesions Mistaken for Sunspots
The belief that sunspots are raised is typically due to misidentification with other common skin growths that develop in similar, sun-exposed locations. The two most frequent culprits are seborrheic keratoses (SKs) and actinic keratoses (AKs), which have distinct appearances and different medical significance.
Seborrheic Keratoses (SKs)
Seborrheic keratoses are benign growths that can appear in areas of sun exposure, but they are not directly caused by UV radiation. These lesions are raised and often described as having a “stuck-on” or waxy appearance, as if a piece of candle wax was dropped onto the skin. They can vary significantly in color, from light tan to dark brown or nearly black, and their surface texture may be rough, crumbly, or slightly greasy to the touch. These are usually harmless, though their raised nature and dark pigmentation often cause alarm and lead to them being mislabeled as a raised or evolving sunspot.
Actinic Keratoses (AKs)
In contrast, actinic keratoses are directly caused by chronic sun damage and represent pre-cancerous lesions. These growths are typically small, rough, and scaly patches that feel like sandpaper when touched, often more easily felt than seen. While they can be skin-colored, pink, or reddish-brown, they are often slightly raised or thickened and may develop a crusty surface. AKs are significant because they carry a small risk of transforming into squamous cell carcinoma, a form of skin cancer, if left untreated.
The key difference lies in their potential risk: SKs are generally harmless, while AKs are a marker of significant sun damage and a precursor to cancer. Because it can be difficult for an untrained eye to distinguish between these growths, any new or changing raised lesion requires professional evaluation.
Warning Signs and When to Consult a Dermatologist
Evaluating a spot for potential concern requires focusing on changes and irregularity, rather than just whether it is flat or raised. Dermatologists use the well-established ABCDE criteria to evaluate pigmented lesions for signs that may indicate melanoma, the most serious type of skin cancer.
The ABCDE criteria are:
- Asymmetry: One half of the spot does not match the other half in shape.
- Border irregularity: The edges are ragged, notched, or blurred rather than smooth and well-defined.
- Color variation: Multiple colors are present within the same lesion, such as shades of tan, brown, black, white, red, or blue.
- Diameter: Any spot larger than six millimeters (roughly the size of a pencil eraser) warrants attention, though melanomas can be smaller.
- Evolving: This is perhaps the most crucial warning sign, referring to any change over time in a spot’s size, shape, color, or texture.
A previously flat spot that becomes raised, or a raised spot that begins to itch, bleed, or crust, falls under the category of evolving and demands immediate medical consultation.
Any new or existing lesion that exhibits any of the ABCDE warning signs should be examined by a healthcare professional. Although solar lentigines are benign, their presence indicates significant UV exposure, which increases the overall risk for all forms of skin cancer. A dermatologist can use a specialized tool called a dermatoscope to examine the spot closely, often determining its nature without the need for a biopsy. Monitoring your skin regularly and seeking prompt evaluation for any suspicious changes is the best defense against skin cancer.