Seborrheic keratosis (SK) is a common skin growth, especially with age. They are non-cancerous and pose no health threat. A common question is whether SK can become cancerous. This article explores SK’s nature, characteristics, and relationship with skin cancer.
Understanding Seborrheic Keratosis
They can arise on almost any part of the body, including the face, scalp, chest, and back, but typically do not appear on the palms or soles of the feet. They vary in color (tan, brown, black, yellow, or gray).
Their texture can be smooth, waxy, or wart-like, often appearing “stuck-on” the skin. Seborrheic keratoses can be flat or raised, measuring from a millimeter to several centimeters in diameter. While they are generally harmless, some individuals may develop hundreds of them.
Seborrheic Keratosis and Cancer Risk
Seborrheic keratosis is a benign skin growth that does not transform into skin cancer. It is not a risk factor for developing skin cancer, nor does it cause skin cancer.
It is extremely rare for a cancerous lesion, such as basal cell carcinoma, squamous cell carcinoma, or melanoma, to mimic seborrheic keratosis. It is also uncommon for skin cancer to coexist within a seborrheic keratosis. SK itself is not precancerous and remains a harmless growth.
How to Differentiate From Other Skin Growths
Distinguishing seborrheic keratosis from other skin growths, especially cancerous ones, is important. While seborrheic keratoses have a uniform appearance, stable size, and distinct “stuck-on” texture, cancerous lesions often display different characteristics. For melanoma, healthcare providers use the ABCDE rule to identify suspicious changes:
- Asymmetry: One half of the growth does not match the other.
- Border irregularity: Edges are often ragged, notched, or blurred.
- Color variation: Multiple shades of brown, black, or even red, white, or blue within the same lesion.
- Diameter: Melanomas are often larger than 6 millimeters, roughly the size of a pencil eraser, though they can be smaller.
- Evolving: Any change in size, shape, color, or symptoms like itching or bleeding over time.
Basal cell carcinoma and squamous cell carcinoma, other types of skin cancer, may appear as pearly or waxy bumps, red scaly patches, or sores that do not heal.
When to Consult a Doctor
Seeking professional medical evaluation for any new or changing skin growth is a sensible approach. A dermatologist can often identify a seborrheic keratosis by visual examination alone. If there is any uncertainty, a doctor may use a dermatoscope, a specialized magnifying tool, for a closer look.
A biopsy (removing a small sample for laboratory analysis) may be performed if cancer is suspected. It is advisable to consult a doctor if a skin growth changes in size, shape, or color, or if it begins to itch, bleed, or cause pain. Any new lesion that appears suddenly or any existing growth that causes concern should also prompt a visit to a healthcare provider.