Nevus melanocytic (overview) D22.-

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 19.12.2022

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Synonym(s)

Birthmark; common melanocytic nevus; melanocytic nevus; Melanocytic nevus; more junctional nevus; Naevocyte nevus; Nevuscellnaevus; Nevus melanocytic; nevus naevocellularis; nevus pigmentosus; nevus pigmentosus naevocellularis; Pigmentation spot; Pigment mark; Pigment tumour

Definition
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Benign, congenital or acquired, melanocyte-derived, brown to brown-black, less commonly reddish or skin-colored, patchy, nodular, plaque-like, or nodular melanocytic nevi that are usually plural but may also be solitary.

Melanocytic nevi may be confined to the epidermis(lentigo simplex, junctional melanocytic nevus), localized in the epidermis and dermis (compound type of melanocytic nevus), or localized exclusively in the dermis (dermal melanocytic nevus). This clinical/histologic typing denotes a sequential developmental process that all melanocytic nevi undergo in stages.

Classification
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Classification of congenital and acquired melanocytic nevi according to histological and clinical criteria:

Etiopathogenesis
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It has been postulated that melanocytic nevi originate from cells migrating from the neural crest into the epidermis. It is likely that melanocytes and "nevus cells" represent identical cell populations, so that the term "nevus cell" can be dispensed with in connection with melanocytic nevi (aka nevus cell nevus).

Localization
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On the whole integument, also on superficial mucous membranes possible.

Histology
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Histologically, 3 variants can be distinguished:

  • Junction type (epidermal initial stage)
  • Compound type (epidermo-dermal)
  • Dermal type: dermal melanocytic nevus.

Melanocytic nevi show intraepidermal and/or dermal accumulations of melanocytes. Melanocytes within the junctional zone have a round, oval, or spindle-shaped appearance and are located in contiguous nests. In the superficial dermis, the cells generally have an epithelioid cellular character with medium-sized, usually centrally located nuclei, and a distinct cytoplasmic rim. The degree of pigmentation is variable, either finely granular but also scollic across the cytoplasm. The nuclei show a uniform chromatin distribution with a slightly clumped texture. Deeper in the dermis, melanocytes lie in strands. Often, the cells show decreased cytoplasmic content. They then resemble lymphocytes and are often arranged in linear strands but also diffusely. The skin appendages are sheathed by the dermal melanocytes, but always remain intact.

Literature
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  1. Sheaf C (1992) Sun and malignant melanoma. dermatologist 43: 251-257
  2. Hesse G et al (1994) Microfilm documentation in the follow-up of melanocytic tumors. dermatologist 45: 532-535
  3. Maitra A et al (2002) Loss of heterozygosity analysis of cutaneous melanoma and benign melanocytic nevi: laser capture microdissection demonstrates clonal genetic changes in acquired nevocellular nevi. Hum Pathol 33: 191-197
  4. Ruiter DJ et al (2003) Current diagnostic problems in melanoma pathology. Seminar Cutan Med Surg 22: 33-41
  5. Schulz H (1992) Reflected light microscopic score for the differential diagnosis of dysplastic nevi. dermatologist 43: 487-490
  6. Schulz H (1994) Reflected light microscopic criteria of benign melanocytic pigment moles of the skin. Nude Dermatol 20: 2-6
  7. Synnerstad I et al (2004) Fewer melanozcytic nevi found in children with active atopic dermatitis than in children without dermatitis. Arch Dermatol 140:1471-1475
  8. Tomita K et al (1998) A nevocellular nevus consisting mostly of nevic corpuscles. J Dermatol 25: 134-135

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Last updated on: 19.12.2022