Nevus melanocytic dysplastic D48.5

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 11.01.2021

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Synonym(s)

Atypical nevus cell nevus; Clark-Naevus; Dysplastic birthmark; Dysplastic melanocytic nevus; Dysplastic nevus; Dysplastic pigment nevus; nevus dysplastic

Definition
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Controversial term for a clinically conspicuous melanocytic nevus (see ABCD rule) with an increased probability of transformation into a malignant melanoma.

To date, there are no generally accepted histological, reflected-light microscopic or clinical features that allow an exact definition of melanoma precursors. If the corresponding range of criteria is insufficient or appears doubtful for an assessment of tumour fitness, the practical benefit of retaining the term dysplasia is that either close follow-up examinations or histological revisions are required for already excised lesions.

If a patient has a large number of such atypical melanocytic nevi, the syndrome of atypical dysplastic nevi is present (see BK-Mole syndrome).

Classification
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Depending on the degree of development can be divided into:
  • Junction-type dysplastic nevus
  • Compound-type dysplastic nevus.

Occurrence/Epidemiology
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Incidence: 100-150/100.000 inhabitants/year. The prevalence of dysplastic nevi is estimated at 1.8-4.6% of the population.

Manifestation
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Mostly occurring after puberty, until the age of 20.

Localization
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Whole integument; preferentially occurring on chest and back, arms and head. In colored people dysplastic nevi occur mainly on the acra and the mucous membrane.

Clinical features
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Usually 0.6-1.5 cm large, blurred, often polycyclically limited, reddish-brown to brown-black coloured spots, papules or plaques with unchanged or also parchment-like, atrophic surface. Reflected light microscopy: see table 1, see below Tab. 2.

Histology
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  • Junction-type dysplastic nevus: The surface epithelium is mostly acanthotic. Reteleases are unevenly or broadly dilated. In the junctional zone, nests arranged at irregular intervals, but also individually distributed (epitheloid) melanocytes are visible. More rarely, nests or melanocytes are also found suprabasally. Melanocyte nests tend to confluence (bridging). Occasional signs of atypia. Occasional round cell infiltration of the upper dermis. Pigment incontinence may be present.
  • Dysplastic nevus of compound type: Mostly symmetrical melanocytic tumor with epidermal and dermal parts. In some places the junctional activity exceeds the dermal part of the tumor (shoulder formation). The epidermal changes correspond to the junctional type. In the dermal parts a maturation of the melanocytes towards depth is detectable. In addition, stroma reactions such as concentric or lamellar fibroplasia occur. Bulky round cell infiltrates.

Diagnosis
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The gold standard is histology.

Incidentlight mic roscopy: Incident light microscopic features, which are otherwise only found in malignant melanomas, reach a proportion of about 14% in the group of dysplastic nevi. The vast majority of melanocytic naevi classified as dysplastic show reflected-light phenomena, as they also occur in ordinary naevi, but often in stronger expression, different frequencies and multicomponent structures. The diagnosis can be standardized by means of an evaluation protocol (see Table 1).

Therapy
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It is important to differentiate between simple and dysplastic nevi using clinical and reflected light microscopy (see table). Dysplastically classified nevi are excised without a safety margin and histologically controlled. In case of a malignant melanoma further procedure see there. In patients with dysplastic nevi in families with BK-Mole syndrome or FAMM syndrome there is an eminently high risk for the development of a malignant melanoma (see there). To reduce the risk of further dysplastic melanocytic nevi, preventive measures are important, see below. Nevus, melanocytic.

Progression/forecast
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Probability of transition to malignant melanoma is increased: According to studies, the risk of melanoma in the presence of a dysplastic melanocytic nevus is about twice as high as normal, in 10 or more dysplastic nevi about 12 times higher, in > 50 nevi about 15-20 times higher than normal.

Tables
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Reflected light microscopic vital histological evaluation protocol for dysplastic melanocytic nevi (according to Schulz)

Feature

Point value

Multiple unstructured grey pigment densifications (> 0.35 mm)

11

grey-blue/yellowish-brown saccular pattern

11

Whitish or bluish opaque veil

10

Melanophagen pseudotrabecula (in the face)

10

Deeply localized gray-blue/ -brown mesh fragment

10

Blood leaks from vascular ectasia

8

Grey-blue globules and rods (> 0,15 mm) or areas with strongly pigmented centropapillary globules

7

Alabaster gypsum lacunae

7

Regression zones with marginal melanophages

7

Angiectatic basic pattern with punctiform or polymorphic vessels

7

White-opaque septa

5

blue-in-pink area

5

Area with evenly distributed capillaries

5

Pseudopodia-like marginal zone

5

Radial straming (digitiform extensions)

5

Brown/black dot in front of blue-grey background

5

Abrupt loss of pigment in the trabeculae

3

Grey-blue dendritic trabecula

3

Grey-blue shadow in pink

3

Multi-component structure (> 2)

3


Incident light microscopic criteria for the differentiation between junctional and dysplastic nevus (modified according to Schulz)

Junior Nevus

Dysplastic nevus

Basic pattern predominantly from one component

+

Symmetrical pigment distribution

++

Multi-component structure

++

Basic pattern predominantly reticular

++

+

Diffuse basic pattern

+

Basic global pattern

+

grey-blue/black centropapillary globules

+

Areas of irregular grey-blue to black pigmented globules

++

Centropapillary brown pigment

++

Massive central symmetrical pigment ejection

+

Bizarre mesh pattern

++

Central underlying grey/blue to grey-black pigment

+

++

Dendritic gray-blue trabecula

++

Abrupt pigment breaks off in trabeculae

++

Melanophageal Trabecula

+

regression araeals with marginal greyish-purple melanophagus clusters

++

Area with uniformly arranged capillaries

+

Literature
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  1. Ackerman AB, Massif D, Nielsen TA (1999) Dysplastic nevus. Atypical mole or typical myth? Ardor Scribendi, Philadelphia
  2. Braun-Falco M et al (2003) Histopathological characteristics of small diameter melanocytic naevi. J Clin Pathol 56: 459-464
  3. Burroni M et al (2005) Dysplastic naevus vs. in situ melanoma: digital dermoscopy analysis. Br J Dermatol 152: 679-684
  4. Farrahi F et al (2005) Histologic similarities between lentigo maligna and dysplastic nevus: importance of clinicopathologic distinction. J Cutan pathogen 32: 405-412
  5. Happle R (1989) Gregor Mendel and the Dysplastic Nevi. dermatologist 40: 70-76
  6. Kint A (1986) The dysplastic nevus syndrome. Z Hautkr 61: 595-598
  7. Naeyaert JM et al (2003) Clinical practice. Dysplastic nevi. N Engl J Med 349: 2233-2340
  8. Roesch A et al (2003) The dysplastic nevus. Separate entity, melanoma precursor or diagnostic dilemma? dermatologist 54: 871-883
  9. Schulz H (1992) Reflected light microscopic score for the differential diagnosis of dysplastic nevi. dermatologist 43: 487-490
  10. Schulz H (1996) Dysplastic nevi in the reflected light microscopic differential diagnosis of malignant melanomas. dermatologist 47: 109-113
  11. Schulz HK (1994) Reflected light microscopic criteria of benign melanocytic pigmented moles of the skin. Nude Dermatol 20: 2-6

Disclaimer

Please ask your physician for a reliable diagnosis. This website is only meant as a reference.

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Last updated on: 11.01.2021