A17. Pigmented naevi

A nevus is a benign lesion of melanocytes in the skin or oral mucosa
Can be pigmented or non-pigmented (most are pigmented)
Histological classification
- Junctional nevi
  - Flat, well-demarcated brown macules
  - Grows in the epidermis at the dermal-epidermal junction
- Compound nevi
  - Elevated
  - Grows in the epidermis at the dermal-epidermal junction and in the dermis
- Dermal nevi
  - Elevated
  - May be hard and grow hair
  - Grows in the dermis only
Clinical classification
- Congenital
  - Small (< 1,5 cm)
  - Medium
  - Giant (> 20 cm)
- Acquired
  - Common acquired nevus
    - < 6 mm
    - Symmetric
    - Homogenous surface
    - Even pigmentation
    - Round or oval shape
    - Sharply demarcated border
  - Atypical/dysplastic nevus
    - Share some similarities to melanoma
    - Must be differentiated from melanoma
    - Fried egg or target-shaped
    - May evolve
    - Atypical colour
    - Irregular, poorly demarcated
  - Spitz nevus
    - Not brown, rather pink, tan, red, etc.
    - In children
  - Halo nevus
    - Nevus surrounded by halo of depigmentation
  - Reed nevus
    - Very dark
    - On limbs
  - Nevus spilus
    - Tan macule speckled with smaller, darker macules
  - Blue nevus
Dysplastic nevus syndrome
- Also called familial atypical multiple mole and melanoma syndrome (FAMMM)
- High number (> 50) of common and atypical nevi and family history of melanoma
- Almost 100% of developing melanoma
Diagnosis
- History
  - Family history?
  - History of skin lesions?
  - History of sunburns?
  - When did nevus appear?
  - Has it changed?
- Physical examination
  - Assess skin type
  - Examination with dermoscope
  - ABCDE
  - Ugly duckling sign