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Melanoma specific structures:
Almost all melanomas will reveal at least one of the following structures/features:
- Atypical network
Typical network consists of brown lines with minimal variability in their color and thickness. The holes of the network are of similar size. Atypical network consists of lines with increased variability in color and thickness. The atypical lines are often broadened, smudgy in appearance and often have a grayish color.
- Angulated lines
- Negative network
- Atypical streaks
Typical streaks consist of streaks arranged symmetrically around the entire perimeter of the lesion as seen in Reed’s nevi.
Atypical streaks consist of streaks that are only focally present at the periphery.
- Atypical dots and globules
Typical dots consist of dots that are centrally located within an otherwise organized lesion or dots associated with a typical network. The typical dost associated with a typical network are located on the network lines on in the holes of the network. Any other manifestation of dots is considered atypical.
Atypical dots are distributed asymmetrically, are not clustered in the center and are associated with an atypical network. Typical globules are those found in nevi described in step-1 of this algorithm. Globules of similar shape, size and color distributed throughout the lesion (including cobblestone), at the periphery of an otherwise reticular nevus, or in the center of an otherwise reticular pattern nevus are considered typical.
Any other manifestation of globules would be considered atypical.
- Peripheral tan structureless areas
- Atypical blotches
Typical blotch consists of one round to oval homogeneous blotch in the center of an otherwise reticular pattern nevus.
Atypical blotch consists of an off center blotch or the presence of multiple blotches. The blotches can have irregular shapes and hues.
- Multiple small hyperpigmented areas of irregular shape
- Accentuated skin markings
- Blue-white veil over raised areas
- Regression structures (flat, non-palpable areas)
- Granularity / peppering
- Scar lie depigmentation
- Blue-white veil over flat area
- Shiny white lines
- Comma vessels in flat lesions (not IDN)
- Dotted vessels
- Serpentine or linear vessels
- Milky red areas and globules
- Polymorphous pattern. The most common pattern is one with both dotted and serpentine vessels
- Corkscrew vessels
Melanoma patterns on Special sites: (see specific chapters for details)
Volar: melanomas on the palms and soles
- Parallel ridge pattern
- Atypical fibrillar pattern
- Diffuse pigmentation with multiple shades of brown
- Multi-component pattern
- Annular-granular pattern
- Asymmetric follicular openings
- Gray dots/granules around ostial openings
- Circle within circle sign
- Angulated lines forming rhomboids
The presence of melanin inclusions defines the lesion as melanocytic. These lesions consist of melanocyte activation as seen in lentigo or melanocytic proliferation as seen in nevi and melanoma. While evaluating the nail plate it is important not to overlook evaluating the paronychia (micro-Hutchinson’s sign) area and hyponychial skin (parallel ridge pattern will be seen).
- Atypical bands
consisting of lines of different colors and thicknesses. The bands may lose their parallelism and appear to converge distally creating a triangular appearance to the band (wider at proximal end and narrow at the distal end)
The features to define early mucosal melanoma have not yet been elucidated. Clearly any lesion with a multi-component pattern should be viewed with suspicion. In addition, any lesion manifesting the colors blue, gray or white should be view with concern for melanoma.