Malignant melanoma Summary Skin Pigmentation Pigmentation of the skin can be endogenous or exogenous in origin. The skin may be penetrated by materials in the environment and cause either accidental or artistic tattooing. Melanin Melanin is a spontaneous condensation product of dopamine metabolism. It is produced by melanocytes which store it and donate it to epidermal cells.
Melanocytes are dendritic and are distributed roughly one per six basal cells.
They are located at the dermo-epidermal junction except on the soles of the feet and palms of the hands. Albinos have defects in melanin production. Vitiligo is due to focal destruction of melanocytes by auto-immune processes. Melanocytes migrate to the skin from the neural crest at the 13th week of embryonic life. Blue naevi are accumulations of dendritic melanocytes in the dermis thought to be due to arrested migration.