Skin-melanocytic tumor
Nevi
Dysplastic nevus

Author: Christopher Hale, M.D. (see Authors page)

Revised: 21 February 2017, last major update September 2014

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed Search: Dysplastic nevus
Cite this page: Dysplastic nevus. PathologyOutlines.com website. http://pathologyoutlines.com/topic/skintumormelanocyticdysplasticnevus.html. Accessed May 29th, 2017.
Definition / general
Terminology
  • Also called atypical nevus, nevus with architectural disorder, nevus with architectural disorder and cytologic atypia, Clark’s nevus
Epidemiology
Clinical features
  • Atypical due to size > 5 mm, irregular borders and variegated appearance
Case reports
Treatment
  • Initial diagnostic biopsy should sample entire lesion (Australas J Dermatol 2005;46:70)
  • Mildly atypical nevi are considered benign and no additional treatment is necessary
  • Severely atypical nevi are excised with negative margins
  • No consensus on moderate atypia; most physicians re-excise if possible if margins are positive
Dermoscopy
  • Pigment patterning often disrupted with brown dots, frequently erratically placed
  • Nevi often irregular in shape, asymmetric, with variable coloration and borders that vary from sharply to poorly defined
Dermoscopic images

Images hosted on other servers:

Dysplastic pointillist nevi with
multiple brown dots on an
erythematous background
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"Diffuse and patchy" network pattern

Clinical images

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Agminated atypical nevi

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Agminated atypical nevi on right arm

Multiple melanocytic
nevi (anterior chest
and abdomen)

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Various images


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Minimal change in a clinically dysplastic nevus

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Evolving and regressing clinical dysplastic nevus

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Development of a clinically dysplastic nevus

Microscopic (histologic) description
  • Compound nevi with marked lentiginous proliferation of melanocytes at dermoepidermal junction, extending at least 3 rete ridges beyond lateral margins of dermal component
  • Nests have cytologic and architectural atypia, including irregular sizes and shapes and bridging of adjacent rete ridges, which are irregular themselves
  • Papillary dermal lamellar fibroplasia with perivascular infiltrate and vascular dilation
  • Usually mild / moderate cytologic atypia (nuclear hyperchromasia, prominent nucleoli, dusty melanin pigment)
  • Melanocytes are spindled and parallel to surface or epithelioid
  • Epidermolytic hyperkeratosis present but not specific (Am J Dermatopathol 2002;24:23)

  • Mild atypia:
    • At high power, nuclei of melanocytes are condensed, oval / ellipsoid, hyperchromatic, indented and have no / small nucleoli
    • Perinuclear halo common; no / minimal pagetoid upward migration of melanocytes
    • No mitotic figures in dermal component

  • Moderate atypia:
    • At high power, nevus nuclei are variable in size and chromatin, although some have "mild atypia" plus small nucleoli
    • Enlarged cytoplasm compared to melanocyte, no halo
    • Few but normal mitotic figures in upper dermal part of nevus

  • Severe atypia:
    • Usually asymmetrical, but still well-circumscribed in epidermis
    • Usually nests of nevus cells, not individual cells
    • Some central upward migration of individual nevus cells
    • Crowded nests in dermis
    • Enlarged nuclei, often bizarre hyperchromatic nuclei mixed with small nuclei and prominent nucleoli
    • No confluent atypia as seen with melanoma; frequent mitoses in junctional component, but not in deep dermal component
    • Note: grading is not consistent between pathologists (Br J Dermatol 2006;155:988)

  • Children:
    • May want to downgrade atypia since ordinary childhood nevi have large nests and large nevus cell size, as well as focal atypia

  • Pagetoid upward migration at periphery:
    • May suggest upgrading to melanoma in situ

  • Mitotic figures at base of dermal component::
    • Suggests invasive melanoma
Microscopic (histologic) images

Images hosted on Pathout server:
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Clark's nevus



Images hosted on Flickr:
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Dysplastic nevus


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Contributed by Dr. Asmaa Gaber Abdou



Images hosted on other servers:

Dysplastic nevus

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Pointillist dysplastic nevus with cytologic atypia

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Strong BRMS1 (A); weak Cul1 (B)

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Lentiginous melanocytic
proliferation with papillary
dermal fibrosis

Positive stains
Molecular / cytogenetics description
Electron microscopy description
  • Cases with severe dysplasia share several features with radial growth phase melanomas, including large cell size, bizarre shaped and pleomorphic nuclei, well developed Golgi, abundant and deranged mitochondria, aberrant melanosomes with deranged structures and irregular melanization
Differential diagnosis