<\/span><\/h2>\nAcquired melanoyctic nevus or mole is common benign<\/span> tumor<\/span>, which usually appears during childhood and adolescence. Sun exposure is a causal factor, particularly in childhood. A point mutation<\/span> at BRAF<\/span> gene<\/span> (most often v600E) is usually the starter genetic<\/span> mutation. The lesions evolve with age, the initial injury<\/span> being macular<\/span> with nests proliferating<\/span> melanocytes<\/span> confined to the dermoepidermal junction. Over time, the nests spread towards the dermis<\/span> and injuries increase. With further maturation of the junctional activity, it ceases and the nevus becomes intradermal<\/span>.<\/p>\nMany melanocytic naevi<\/span> eventually returns and the number of nevi decreases with the age of 50 years.<\/p>\nThe classification of common acquired nevi is based primarily on the location of the nests (e.g., union, compound, dermal<\/span> or combined nevi) leading to features that are often clinically recognizable. Dermatoscopy is also useful in classifying nevi, especially when there are atypical<\/span> clinical features that raise suspicion of melanoma<\/span>.<\/p>\n<\/span>Union nevi<\/span><\/h2>\nJunctional nevi are generally pigmented<\/span> macules<\/span> in clinical examination. Histologically<\/span>, proliferating melanocytes are found at the dermoepidermal junction. The cells within the nests are oval or cuboidal in shape, with a clear cytoplasm<\/span> and variable pigmentation<\/span> (Figure 1).<\/p>\n\n<\/span>Junctional melanocytic nevus pathology<\/span><\/h5>\n<\/section>\n\n\n
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Figure 1<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>Compound nevus<\/span><\/h2>\nCompound melanocytic nevi have a raised central area with surrounding flat pigmentation. the epidermis<\/span> may be normal in appearance, acanthotic or visualization seborrheic<\/span> keratosis<\/span>-like changes. Melanocyte nests are found at the dermoepidermal junction and within the dermis. Melanocytes exhibit maturation as they become deeper and tend to be smaller with less pigmentation. (Figures 2, 3).<\/p>\n\n<\/span>Melanocytic pathology composed of nevus<\/span><\/h5>\n<\/section>\n\n\n
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Figure 2<\/p>\n
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figure 3<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>Intradermal nevi<\/span><\/h2>\nIntradermal nevi are dome-shaped, nodular<\/span> or polypoid lesions that may become unpigmented, particularly on the face. Melanocyte nests are confined to the dermis. Melanocytes can show 'pseudo-inclusions<\/span>', which are invaginations of cytoplasm in the core<\/span> giving the appearance of nuclear<\/span> inclusions or cells with multiple nuclei<\/span>. Deeper, the cells of the nevus may become spindle-shaped or \u201cneurotized.\u201d Fatty differentiation<\/span> It is not strange. Bone formation is a very rare finding in common nevi (Nanta nevi) (figure 4).<\/p>\n\n<\/span>Pathology of intradermal nevus<\/span><\/h5>\n<\/section>\n\n\n
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Figure 4<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>Meyerson naevus<\/span><\/h2>\nMeyerson's neevus has a eczematous<\/span> halo surrounding a junctional, compound, or intradermal nevus. There's a concurrent<\/span> subacute finding spongy<\/span> dermatitis<\/span> with a melanocytic nevus (figure 5).<\/p>\n\n<\/span>Meyerson naevus pathology<\/span><\/h5>\n<\/section>\n\n\n
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Figure 5<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>Balloon cell nevus<\/span><\/h2>\nBalloon cells are large nevus cells with clear cytoplasm. A balloon cell nevus is usually diagnosed when more than half of all nevus cells within a lesion are balloon cells. Clinically these lesions are not distinctive (figure 6).<\/p>\n\n<\/span>Nevus balloon cell pathology<\/span><\/h5>\n<\/section>\n\n\n
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Figure 6<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>Returning naevi<\/span><\/h2>\nMelanocytic nevi may eventually return; nevus cells being replaced by collagen<\/span>, fat, elastin<\/span> and soil substance<\/span> (figure 7, nevus with fat and neural metaplasia<\/span>)<\/p>\nRegression<\/span> can be announced by lymphocytic<\/span> Destruction of nevus cells giving rise to a nevus halo. In these lesions, the dermis shows dense lymphocytes. infiltrators<\/span> surrounding nests of melanocytes (figures 8, 9). Due to the infiltrate<\/span>Obfuscation of the melanocytic lesion, evaluation of the cytology<\/span> Sometimes it can be a challenge. Clinically, there is a halo of depigmentation<\/span> surrounding one or more nevi. Halo naevi may be associated with vitiligo.<\/p>\n\n<\/span>Regression of melanocytic pathology of nevi<\/span><\/h5>\n<\/section>\n\n\n
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Figure 7<\/p>\n
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Figure 8<\/p>\n
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Figure 9<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>Site-specific characteristics of melanocytic nevi<\/span><\/h2>\nBenign melanocytic naevi at various sites may show unusual histopathological<\/span> characteristics that can mimic melanoma.<\/p>\nNevi of the auricular region, breast, conjunctiva<\/span> and the ankle sometimes have an atypical appearance proliferation<\/span> of melanocytes in the epidermis, often with pagetosis and cytology atypia<\/span>. Some features seen in dysplastic<\/span> nevus as lamellar