Skin & Soft Tissue: Melanocytic Nevus (Mole)

Melanocytic Nevus (Mole)

Definitions

  • Melanocytic Nevus: Benign Proliferation of Nevus Cells (Type of Melanocyte Clustered in Nests)
  • Congenital Melanocytic Nevus: Present at Birth or First 6 Months of Age
    • Extend Deeper than Acquired Melanocytic Nevi
  • Acquired Melanocytic Nevus: Appear After 2 Years of Age

Congenital Melanocytic Nevus (CMN)

Presentation

  • Pigmented Lesion
  • Macules or Slightly Raised Papules
  • Sharply Demarcated Borders
  • Grow Proportionally with the Child – Cover the Same Relative Surface Area Throughout Growth
  • Occur in Any Location
  • Giant Lesions May Have a “Garment”/“Bathing Trunk”/“Coat Sleeve” Appearance Due to Large Surface Area Resembling Clothing
  • Large-Giant Lesions Often Have Other Surrounding Satellite Lesions

Classification

  • Size:
    • Small: < 1.5 cm
    • Medium: > 1.5 cm
      • M1: 1.5-10 cm
      • M2: 10-20 cm
    • Large: > 20 cm
      • L1: 20-30 cm
      • L2: 30-40 cm
    • Giant: > 40 cm
      • G1: 40-60 cm
      • G2: > 60 cm
    • *Based on the Projected Largest Diameter Achieved by Adulthood
      • Estimated Size Increase:
        • Head: 1.7x
        • Trunk/Arms: 2.8x
        • Legs: 3.3x
  • Satellite Lesions (Used to Further Classify Large-Giant Lesions):
    • S1: 0
    • S2: 1-19
    • S3: 20-50
    • S4: > 50

Melanoma Risk

  • Small-Medium Sized: < 1%
  • Large-Giant: 2-5%
    • Half of the Risk is During the First Five Years of Life

Diagnosis

  • Mostly Clinical (Based on History and Physical Exam)
  • May Consider Skin Biopsy to Rule Out Malignancy

Treatment

  • Small-Medium: Periodic Monitoring
    • Excision Indications:
      • Difficult Site to Monitor for Changes
      • Parent Preference (Cosmesis or Anxiety)
  • Large-Giant: Surgical Excision
    • May Be Difficult-Impossible to Completely Excise
    • May Require Skin Grafting

Congenital Melanocytic Nevus 1

Giant Congenital Melanocytic Nevus 2

Acquired Melanocytic Nevus (AMN)

Presentation/Types

  • Common (Banal)
    • Pigmented Lesion
    • Symmetric
    • Homogenous Surface
    • Round with Sharply Demarcated Borders
    • Small (≤ 6 mm)
  • Atypical
    • Share Clinical Features of Melanoma (Asymmetric, Border Irregular, Color Variation or Diameter > 6 mm)

Diagnosis

  • Mostly Clinical (Based on History and Physical Exam)
  • May Consider Skin Biopsy to Rule Out Malignancy
  • A Nevus with Different Features from Other Nevi (“Ugly Duckling”) Raises Concern for Melanoma

Treatment

  • Common (Banal): Periodic Monitoring & Sun Protection
    • Consider Excision for Patient Preference (Cosmesis)
    • No Benefit to “Prophylactic” Removal – Most Melanomas Arise De Novo
  • Atypical: Excisional Biopsy
    • Re-Excision of Positive Margins is Debated

Acquired Melanocytic Nevus 3

References

  1. Sand M, et al. Wikimedia Commons. (License: CC BY-2.0)
  2. Sharma S, et al. Wikimedia Commons. (License: GNU FDL)
  3. National Cancer Institute. Wikimedia Commons. (License: Public Domain)