Epidemiology

Etiology

Melanocyte is in the stratum basale of the skin

UV radiation exposure
Light skin types
Genetic mutations, including:
- BRAF gene mutations
  - Seen in 50% of melanomas
  - V600E mutation (most common): an activating mutation in the BRAF gene that substitutes glutamic acid for valine at amino acid position 600
- CDKN2A gene mutations

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A = Asymmetry
B = Border (irregular border with indistinct margins)
C = Color (variegated pigmentation within the same lesion)
- Red areas are due to vessel ectasia (dilation) and local inflammation.
- Brown or black, flared areas along the border are due to advancing, neoplastic melanocytes.
- White and gray areas appear when cytotoxic T lymphocytes recognize tumor antigens (eg, melan-A) and induce apoptosis, leading to malignant melanocyte regression (cleared patches).
D = Diameter > 6 mm
E = Evolving (a lesion that changes in size, shape, or color over time)

Histopathology revealed poorly differentiated cells with abundant mitotic activity and necrosis.
Immunostaining was positive for S-100 (a protein expressed in cells derived from the neural crest such as melanocytes) and HMB-45 (a marker for immature melanosomes found in melanocytic tumors) indicating melanoma.
- S-100 is also expressed in Schwannoma