Seborrheic Keratosis

Aka: Seborrheic Keratosis, Seborrheic Keratoses, Stucco Keratoses, Leser-Trelat Sign, Dermatosis Papulosa Nigra

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II. Epidemiology

  1. Most common benign epithelial tumor
  2. More common in patients over age 30 years old
  3. Number of lesions increase with age
  4. Men and women affected equally
  5. Autosomal Dominant inheritance

III. Pathophysiology

  1. Common benign, hereditary tumor composed of Keratinocytes
  2. Hyperkeratotic epidermal lesion

IV. Symptoms

  1. Typically asymptomatic
  2. Pruritus may occur

V. Signs

  1. Characteristics
    1. Early (Flat lesions)
      1. Small (<3mm)
      2. Slightly elevated
      3. Variable hyperpigmented coloration
    2. Late (Raised pigmented lesions)
      1. Large Plaque (1 to 6 cm)
      2. May feel greasy, velvety or warty
      3. Keratotic (warty) appearance
        1. Appears "stuck-on" like clay
        2. Rough surface
      4. Yellow, tan, brown or black pigmentation
      5. Sharp well-circumscribed border
  2. Distribution (typically multiple are present)
    1. Trunk (esp. back, most common location)
    2. Face
    3. Scalp
    4. Upper extremities
  3. Associated lesions
    1. See variants below
    2. Horn cysts
    3. Milia-like cysts
  4. Additional exam measures
    1. Dermoscopy may be useful in differentiating Seborrheic Keratoses from Melanoma

VI. Findings: Variants

  1. Stucco Keratoses
    1. Numerous small white, dry scaly lesions on extremity
  2. Dermatosis Papulosa Nigra
    1. Small, dark Papules seen in darker skin
    2. Photodistribution of lesions (face, head, neck)
  3. Leser-Trelat Sign (paraneoplastic sign)
    1. Sudden onset and increase in number of Seborrheic Keratoses
    2. Requires thorough evaluation for malignancy
    3. Seborrheic Keratoses often resolve with malignancy treatment and reappear with cancer recurrence
    4. Associated with underlying adenocarcinoma
      1. Stomach Cancer
      2. Colon Cancer
      3. Breast Cancer

VII. Differential Diagnosis

  1. Early Seborrheic Keratosis (Flat)
    1. Solar Lentigo
    2. Spreading pigmented Actinic Keratosis
    3. Malignant Melanoma
  2. Late Seborrheic Keratosis (Raised pigmented)
    1. Pigmented Basal Cell Carcinoma
    2. Malignant Melanoma

VIII. Management

  1. Indications for excision
    1. Cosmesis
    2. Local irritation due to recurrent Trauma
    3. Malignancy suspected (Excisional Biopsy needed)
  2. Techniques
    1. Curettage with light Electrocautery
      1. Inject Local Anesthesia first
      2. Lesion easily rubs off
      3. Lightly cauterize base to prevent recurrence
    2. Cryotherapy with Liquid Nitrogen
      1. May not be effective in very thick lesions
      2. Risk of Hypopigmentation (esp. in darker skin)
    3. Excision
      1. Shave Excision
      2. Excisional Biopsy (if possible Melanoma)
    4. Topical Corticosteroids
      1. Indicated for irritated Seborrheic Keratoses

IX. References

  1. Fitzpatrick (1999) Color Atlas Dermatology
  2. Higgins (2015) Am Fam Physician 92(7): 601-7 [PubMed]
  3. Wagner (2024) Am Fam Physician 110(4): 353-61 [PubMed]

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