Etiology and pathogenesis: Melanin in melanocytes and keratinocytes in pigmented spots increases, and melanocytes are hyperactive, producing a large amount of melanin and forming pigmented spots. Coffee spot can be a sign of multi-system diseases, such as neurofibroma, tuberous sclerosis, Albright syndrome, Silver—Russel syndrome and Wat—sons syndrome.
Clinical manifestations: coffee spot nevus is a light brown to dark brown spot or patch, like the mixed color of coffee and milk, so it is also called milk coffee spot, which is round, oval or irregular in shape, with clear boundary and smooth surface. It can appear at birth, or it can appear gradually later after birth, and it will increase throughout childhood. It can occur in any part of the body and does not subside by itself. It is reported that 10%-20% of children have a single coffee spot. More than 90% patients with neurofibroma have coffee spots, so some people think that the existence of neurofibroma should be highly suspected when there are six or more coffee spots with a diameter of 1.5cm.
Histopathology: Histopathology showed that the melanosome of keratinocytes increased, and Fontona—Musson staining showed that the total melanin in epidermis increased, especially in the basal layer. There are huge melanosome in dopa stained melanocytes and keratinocytes in the basal layer. The melanocytes in the basal layer are normal or slightly increased.
Diagnosis and differential diagnosis: according to the characteristics of milk and coffee stains with clear edges, a diagnosis can be made. It must be differentiated from freckles and simple freckled nevus: freckles are small, without large patch damage, mainly on the face. Simple freckle nevus is mostly unilateral local disease. Pathology can also help to differentiate.
Laser treatment: The laser treatment of coffee spots is basically the same as freckles. Any laser that is effective for melanin can be used to treat coffee spots, but it must be treated several times. Satisfactory curative effect can be obtained by using 532nm pulsed dye laser treatment, and pigmentation or decline rarely occurs. It should be noted that the energy density should not be too large during treatment, and the spot test can be done first until the lesion surface turns white.