Seborrheic Keratosis (SK)
Seborrheic keratosis is a benign epidermal neoplasm arising from clonal proliferation of keratinocytes. Clinically, lesions present as well-demarcated, round to oval, slightly elevated macules, papules, or plaques with a classic "pasted-on" appearance. They vary in color—light tan, brown, or black—with waxy, verrucous, or scaly surfaces. Predominantly seen on the trunk, face, neck, or forehead, they spare the palms and soles and increase exponentially with age, affecting the vast majority of individuals over 60 years. Subtypes include acanthotic, hyperkeratotic, clonal, adenoid, irritated, and melanoacanthoma variants, among others.
Symptoms
Seborrheic keratoses are asymptomatic in most cases. Patients present with slowly enlarging or new lesions that may be multiple and in varying colors. Lesions may occasionally itch, bleed if traumatized or irritated by friction, or become cosmetically bothersome. Rarely, abrupt onset of dozens to hundreds of SKs (the Leser–Trélat sign) may herald an underlying malignancy.
Risk Factors
Age remains the strongest risk factor; nearly all individuals over age 60 develop SK, with increasing numbers and sizes over time. UV exposure accelerates lesion formation, particularly on sun-exposed skin. Genetic predisposition is implicated, though inheritance patterns are poorly defined. Light skin phototypes (Fitzpatrick I–III) exhibit higher prevalence. Rare familial syndromes and early-onset variants (e.g., DPN) suggest hereditary components. Other potential associations such as HPV presence, metabolic alterations in lipid and glucose metabolism, and amyloid precursor protein overexpression have been described, though their clinical significance remains unclear .
Diagnosis
Diagnosis is typically clinical, guided by characteristic features: stuck-on appearance, waxy or verruciform texture, and horn cysts visible to the naked eye or dermoscopy (comedo-like openings, milia-like cysts). Dermoscopy enhances diagnostic accuracy. Lesions with atypical features—ulceration, irregular borders, rapid growth, erythema, telangiectasia—or pigmented ones mimicking melanoma or lentigo maligna require biopsy or complete excision for histopathologic evaluation. Histology reveals hyperkeratosis, acanthosis, papillomatosis, keratin cysts, and absence of cellular atypia.
Treatment
Treatment is elective and aimed at relieving symptoms or cosmetic concerns. Common modalities include cryotherapy using liquid nitrogen, curettage or shave excision often combined with electrocautery, and electrodessication alone. For thick or numerous lesions, combination therapies are favored. Laser treatments such as Er:YAG or CO₂ show good efficacy with lower post-procedural pigmentation risk. Topical therapies include imiquimod, tazarotene, alpha-hydroxy acids, and recently FDA-approved hydrogen peroxide 40% solution. Rare and irritative or unusual variants warrant histologic confirmation prior to treatment.
Outlook
SKs are benign with excellent prognosis. Lesions may increase in size or number over time; spontaneous resolution is rare. Recurrence at treated sites is uncommon, although reappearance may necessitate re-biopsy in cases of persistent lesions. Overlapping or collision with malignant lesions such as basal or squamous cell carcinoma has been reported. Leser–Trélat sign may suggest occult malignancy and warrants evaluation .
Complications
Minor complications include post-procedural pigmentation changes, scarring, bleeding, or infection at removal sites. Malignant transformation is extremely rare but possible via collision tumors or lesion misdiagnosis. Leser–Trélat sign can indicate underlying neoplasia.
Prevention
Primary prevention is not established given genetic predisposition and aging etiology. However, minimizing UV exposure through sun protection may reduce lesion formation. Regular skin exams aid in early detection of atypical lesions.
Support
Patients may photograph lesions for monitoring changes over time. Educating on avoiding lesion trauma and recognizing warning signs is essential. For multiple cosmetically concerning lesions, counselling regarding available removal techniques and their risks/benefits is recommended.
Sources
The information presented above is supported by reputable medical sources and research publications. These references provide additional clinical insights and evidence-based findings for healthcare professionals and individuals seeking comprehensive understanding of this medical condition.
