Level 1: Nevi
Step 1:
Level 1: The most common patterns found in nevi (excluding IDN).
Network or reticular pattern:
consists of an organized network with minimal variation in its thickness and color (i.e., regular/typical network). The holes of the network are relatively uniform in their appearance.
Patchy network/reticular pattern:
patches of typical network distributed in an organized manner. The network patches all have the same type of network with minimal variability in the thickness and color of the lines. It is important to remember that melanoma on sun damaged skin can sometimes appear as an isolated large lentiginous lesion with a patchy network. The clues to the diagnosis include the age of the patient since these melanomas occur in the elderly, the network is usually not distributed in an organized fashion, and there is usually focal granularity present.
Peripheral network with central hypopigmentation:
The peripheral network is typical/regular and the central hypopigmented area is lighter in color compared to the network but darker than the surrounding skin.
Peripheral network with central hyperpigmentation.
The peripheral network is typical/regular and the central hyperpigmented area consists of a blotch. This blotch often due to the accumulation of melanin laden corneocytes in the straum corneum (i.e., lamella). This lamella can usually be tape stripped off revealing an underlying typical network.
Peripheral network with central brown globules:
The peripheral network is typical/regular and the central brown globules are also regular displaying minimal variation in their size and color.
Globular pattern:
This pattern consists only of globules that display minimal variability in their sizes and colors (i.e., regular/typical) and are distributed in an organized manner within the lesion. The globules can have different shades of brown. On rare occasion the globules can be white as seen on balloon cell nevi. While black and blue globules can on occasion be seen in congenital nevi, their presence should raise suspicion for melanoma.
Cobblestone globular pattern:
This is a specific type of globular pattern that consists of large brown angulated globules that create a pattern reminiscent of cobblestones. This is a pattern associated with congenital nevi.
Reticular pattern with peripheral globules:
This pattern consists of a typical network nevus that has a peripheral rim of regular brown globules. This pattern is associated with the radial growth phase of Clark’s/dysplastic nevi and is commonly encountered in younger patients with the atypical mole syndrome.
Homogeneous blue:
A homogeneous blue color with a whitish veil that encompasses the entire lesion’s surface is the hallmark of a blue nevus. The blue color and white veil in blue nevi will have minimal variation in hues. If there are multiple hues (i.e, heterogeneous blue color or non-homogeneous veil) then one should consider the diagnosis of melanoma. In addition, the differential for blue nevi should include epidemiologic metastasis and if nodular then one needs to consider the diagnosis of nodular melanoma.
Homogeneous brown:
This pattern consists of a nevus with homogeneous brown color with minimal to no variation in its hues. While it is usually devoid of any other structures, on rare occasions one can see a few regular dots/globules and fragments of network. This pattern is seen in congenital nevi.
