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Keratosis, Seborrheic

Authors: Michael T. Partin, MD; Karl T. Clebak, MD, MHA, FAAFP

BASICS

DESCRIPTION

  • Common benign epidermal tumor due to keratinocyte proliferation
  • Typically appears in multiples, well-circumscribed, yellow to brown, greasy/velvety/warty lesions
  • Described as having a “stuck-on” appearance
  • Spares palms and soles
  • Occurs on hair-bearing skin of older adults
  • Variants:
  • Common seborrheic keratosis
  • Dermatosis papulosa nigra
  • Stucco keratosis
  • Flat seborrheic keratosis
  • Pedunculated seborrheic keratosis

Synonyms: SK, verruca seborrhoica, senile wart, basal cell papilloma, barnacles of aging

EPIDEMIOLOGY

  • Age: Appears 31–50 years; peaks at 60+
  • Sex: Slightly more common in males
  • Most common in Caucasians, except dermatosis papulosa nigra (in darker skin)

Prevalence: - 69–100% of adults >50 years
- Increases with age

ETIOLOGY & PATHOPHYSIOLOGY

  • Etiology unclear: UV exposure & genetics implicated
  • HPV role uncertain
  • Genetics: Suggests autosomal dominant inheritance

RISK FACTORS

  • Advanced age
  • UV light exposure
  • Family history/genetic predisposition

PREVENTION

  • Sun protection may reduce occurrence

ASSOCIATED CONDITIONS

  • Sign of Leser-Trélat:
  • Sudden eruption of multiple SKs → may signal internal malignancy (esp. adenocarcinoma)
  • Rarely: may occur adjacent to cutaneous malignancies
  • SCC, BCC, melanoma

DIAGNOSIS

HISTORY

  • Asymptomatic
  • If irritated: pruritus, erythema, bleeding, pain, crusting

PHYSICAL EXAM

  • Oval/round, flat dull patches → evolve into elevated verrucous plaques
  • Color: Black, brown, tan, grey, white, or skin-colored
  • Size: Several mm to cm (average 0.5–1 cm)
  • Occur as multiples; may exceed 100 lesions
  • Crumble when scratched

Variants:

  • Common SK: waxy/verrucous, “stuck-on”
  • Dermatosis papulosa nigra: small black papules on face/neck, mostly in darker-skinned individuals
  • Stucco keratoses: gray-white papules on lower limbs/forearms (more common in men)
  • Flat SK: tan-brown macules on face/upper trunk
  • Pedunculated SK: hyperpigmented in friction zones (e.g., neck, axilla)

DIFFERENTIAL DIAGNOSIS

  • Pigmented: melanoma, melanocytic nevus, pigmented BCC
  • Lightly pigmented: Bowen disease, fibroma, verruca vulgaris
  • Flat: solar lentigo, verruca plana
  • Hyperkeratotic: actinic keratosis

DIAGNOSTIC TESTS & INTERPRETATION

  • Usually clinical diagnosis
  • Biopsy if:
  • Atypical
  • Rapidly changing
  • Inflamed or bleeding

Dermoscopy findings:

  • Milia-like cysts, comedo-like openings, hairpin vessels, pseudocysts, pigment networks

Histology:

  • Acanthosis, papillomatosis, horn cysts, squamous eddies
  • Hyperpigmentation, basaloid proliferation

TREATMENT

GENERAL APPROACH

  • Not required unless:
  • Cosmetic concern
  • Symptomatic (irritation, bleeding)
  • Concern for malignancy

MEDICATION

  • Not first line
  • HP40 (Eskata) – 40% hydrogen peroxide
  • Recently FDA approved
  • Requires multiple applications
  • Others (limited evidence): tazarotene, diclofenac, imiquimod, calcitriol, dobesilate

SURGICAL/PROCEDURAL OPTIONS

Preferred methods, selected based on lesion type and provider availability:

  • Cryotherapy (liquid nitrogen) – 5–10 sec spray
  • Curettage – scraping with a curette
  • Electrodessication – destroys tissue with electric current
  • Shave excision – scalpel or razor
  • Laser ablation – CO₂ or other
  • Chemical peel – e.g., trichloroacetic acid

Patient preference: cryotherapy favored over curettage in one study due to less wound care, similar cosmetic results.

FOLLOW-UP & MONITORING

  • Not required unless:
  • New or sudden-onset multiple lesions
  • Inflammation or bleeding
  • Change in appearance

PATIENT EDUCATION

  • Emphasize sun protection
  • Skin self-exam if new growths
  • Education resources:
  • https://www.aad.org/public/diseases/bumps-and-growths/seborrheic-keratoses
  • https://www.cdc.gov/cancer/skin/basic_info/prevention.htm

PROGNOSIS

  • Benign
  • Do not transform into malignancy
  • Leser-Trélat sign = potential poor prognosis if related to malignancy

COMPLICATIONS

  • Irritation or trauma from clothing/jewelry
  • Complications of removal: hypopigmentation, scarring, recurrence
  • Misdiagnosis: rare, but consider biopsy if atypical

CODES

  • ICD-10:
  • L82.1 – Other seborrheic keratosis
  • L82.0 – Inflamed seborrheic keratosis

CLINICAL PEARLS

  • SKs are benign, common in aging populations
  • Removal not needed, but many surgical options available
  • Sudden multiple lesions → evaluate for underlying malignancy