Seborrheic Keratosis: Clinical Description and Management
Seborrheic keratosis (SK) is a common, benign epidermal tumor that appears as stuck-on, waxy, keratotic lesions on the skin, affecting approximately 83 million Americans, particularly those over age 50. 1
Clinical Presentation
Appearance: SKs typically present as:
- Well-demarcated, round to oval lesions
- "Stuck-on" appearance (key diagnostic feature)
- Waxy, keratotic texture
- Color ranging from light tan to dark brown or black
- Size ranging from a few millimeters to several centimeters
- May be flat (macular) or raised (papular)
Distribution:
- Can occur on any body site
- Most commonly found on the trunk, face, and extremities
- Multiple lesions are common (33% of patients have more than 15 lesions) 1
Symptoms:
- Usually asymptomatic
- May occasionally become irritated, itchy, or tender if traumatized
Pathophysiology
Risk factors:
- Increasing age (primary risk factor)
- Male gender preponderance
- Ultraviolet exposure (contributes by altering biochemical factors) 2
- Genetic predisposition
Molecular mechanisms:
- Oncogenic mutations involving FGFR-3 and FOXN1 genes
- Possible association with human papillomavirus in genital lesions
- Merkel cell polyomavirus has been detected in some SKs 2
Differential Diagnosis
SKs must be differentiated from:
- Malignant melanoma: Particularly important when SKs are dark or irregular
- Squamous cell carcinoma: When SKs are inflamed or irritated
- Basal cell carcinoma: When SKs have pearly borders
- Actinic keratosis: Pre-malignant lesions that may appear similar
- Pigmented nevi: May resemble early or small SKs
Diagnostic Approach
Clinical examination: Most SKs can be diagnosed visually by their characteristic "stuck-on" appearance
Dermoscopy: A valuable non-invasive tool showing:
- Milia-like cysts
- Comedo-like openings
- Fissures and ridges
- "Brain-like" appearance 3
Biopsy: Indicated when:
- Diagnosis is uncertain
- Lesion shows atypical features (bleeding, ulceration, rapid growth)
- Need to rule out malignancy 4
Management Options
Most SKs do not require treatment unless they:
- Cause cosmetic concerns
- Become irritated or symptomatic
- Require histologic confirmation of diagnosis
When treatment is desired, options include:
Cryosurgery: Most commonly used method 1
- Quick procedure with minimal scarring
- May cause temporary hypopigmentation, especially in darker skin types
Shave excision:
- Provides tissue for histopathologic examination
- Effective for larger or thicker lesions
Electrodessication and curettage:
- Good for multiple or smaller lesions
- May leave hypopigmented areas
Laser therapy:
- Newer option with potentially better cosmetic outcomes
- More expensive than traditional methods
Nanosecond-pulsed electric field technology:
- Promising newer technique with fewer side effects 2
Important Considerations
Malignancy concerns: While SKs are benign, lesions that are inflamed, bleeding, ulcerated, or rapidly changing should be biopsied to rule out melanoma or other malignancies 4
Sign of Leser-Trélat: Sudden appearance of multiple SKs may rarely be associated with internal malignancy and warrants further investigation
Cosmetic outcomes: Treatment selection should consider skin type, as darker skin types are more prone to post-inflammatory hypopigmentation or scarring
Patient education: Patients should be informed about the benign nature of SKs and taught to monitor for concerning changes that would warrant medical attention
Pitfalls to Avoid
- Misdiagnosing melanoma as SK (particularly for dark or irregular lesions)
- Overlooking malignancies arising within SKs
- Unnecessary treatment of asymptomatic lesions
- Aggressive treatment leading to scarring, especially on cosmetically sensitive areas
Proper diagnosis and appropriate management of SKs can provide reassurance to patients while ensuring that potentially concerning lesions receive appropriate evaluation.