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
Pathophysiology
Clinical features
ABCDE criteria
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)
Diagnostics
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.
