Diagnosis

Melanocytic nevi

Etiology

Cause

• Congenital melanocytic nevi: an error in the embryological migration (congenital malformation)

• Acquired melanocytic nevi:

  • Ultraviolet exposure

  • Genetic factors (dysplastic nevus syndrome)

  • Blistering events (thermal burns, toxic epidermal necrolysis, epidermolysis bullosa)

• Dysplastic nevi (Clark nevi): Acquired nevi that are relatively flat, thinly papular, and relatively broad. Precursors to melanoma.

• Spitz nevi: Pink papules on the head of a child. Vascular ectasia display a hemangioma-like appearance.

• Blue nevi: Melanocytic usually pigmented nevi. Because of the presence of deep pigmentation within a the skin, the brownish-black pigment present contributes a bluish cast to such lesions.

Pathophysiology [usz][d4l]

1. Melanocytes are dendritic cells derived from the neural crest present over the entire body surface.

2. Exogenous ultraviolet (UV) irradiation increase the density of melanocytes in normal epithelium

3. Melanocytic nevi represent proliferations of melanocytes that are in contact with each other, forming small collections of cells known as nests

4. These nevi commonly form during early childhood as a response to sun (UV) exposure

5. Genetic factors are also involved in the development of specific melanocytic nevi

Epidemiology

Prevalence per 100.000 [cre]

Approach

• Dermatoscopy:

  • Asymmetry

  • Borders: irregular

  • Color variation

  • Diameter > 6 mm

  • Evolution/elevation of lesion over time

• Biopsy

Treatment

1. Excision

2. Lymph node sampling

Differential diagnoses

Basal cell carcinoma, Malignant melanoma, Pyogenic granuloma