Skin melanocytic tumor

Nevi

Dysplastic nevus



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PubMed Search: Dysplastic nevus

Sepideh Nikki Asadbeigi, M.D.
Cuong Nguyen, M.D.
Page views in 2022: 28,853
Page views in 2023 to date: 2,548
Cite this page: Asadbeigi SN, Nguyen C. Dysplastic nevus. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumormelanocyticdysplasticnevus.html. Accessed January 30th, 2023.
Definition / general
Essential features
  • First described by Clark and colleagues in 1978 (Arch Dermatol 1978;114:732)
  • Dysplastic nevi are characterized by histological, rather than clinical, criteria
  • Although many melanomas arise de novo (without an obvious or detectable precursor lesion), approximately 25% histologically demonstrate an associated melanocytic nevi (J Natl Cancer Inst 2016;108:djw121)
Terminology
ICD coding
  • ICD-O: 8727/0 - dysplastic nevus
  • ICD-10: D22.9 - melanocytic nevi, unspecified
Epidemiology
Sites
Pathophysiology
Etiology
Clinical features
  • Dysplastic nevi are characterized by histologic features; clinically, dysplastic nevi may appear small and banal
  • Atypical nevi demonstrate the following clinical features:
    • Usually > 5 mm
    • Irregular borders
    • Some with a pigmented and erythematous rim
    • Variegated pigmentation with a mixture of pink, light and dark brown
  • Dermoscopy: reticular pattern, dots and clods at the periphery (J Dermatol 2019;46:e76, Dermatol Clin 2016;34:395)
  • Classic dysplastic nevus syndrome:
    • Patients with 100 or more nevi with at least 1 nevus larger than 8 mm and at least 1 nevus with clinical atypical features
    • National Institutes of Health revision: this term should only be used in patients with a positive family history for melanoma (Clinics (Sao Paulo) 2011;66:493)
  • Eruptive atypical nevus may develop after chemotherapy or immunotherapy (Pediatr Dermatol 2007;24:135)
Diagnosis
Prognostic factors
  • Most dysplastic nevi never progress to melanomas even though they are associated with melanomas
  • Several studies suggest that patients with dysplastic nevi demonstrate an increased risk of melanoma, between 4 - 15 fold (J Am Acad Dermatol 2012;67:1.e1)
  • Patients with familial dysplastic nevus syndrome have an increased risk of developing other malignancies, particularly pancreatic cancer (Int J Cancer 2000;87:809)
  • Patients with dysplastic nevi and 2 or more family members with melanoma have a higher risk of melanoma but patients who have a family history of melanoma and no dysplastic nevi are only at an average risk for melanoma (Clinics (Sao Paulo) 2011;66:493)
  • Risk of melanoma increases as the number of dysplastic nevi increase (Melanoma Manag 2016;3:85)
  • Superficial spreading type melanoma is more commonly associated with dysplastic nevus compared with lentigo maligna type melanoma (Arch Dermatol 2003;139:1620)
Case reports
Treatment
Clinical images

Images hosted on other servers:
Dysplastic, pointillist nevi with multiple brown dots

Dysplastic,
pointillist
nevi with multiple
brown dots

Diffuse and patchy network pattern

Diffuse and patchy network pattern

Agminated atypical nevi

Agminated atypical nevi

Agminated atypical nevi on right arm

Agminated atypical nevi on right arm

Multiple melanocytic nevi (anterior chest and abdomen)

Multiple melanocytic nevi (anterior chest and abdomen)


Dysplastic nevus syndrome

Dysplastic nevus syndrome

Minimal change in a clinically dysplastic nevus

Minimal change in a clinically dysplastic nevus

Evolving and regressing clinical dysplastic nevus

Evolving and regressing clinical dysplastic nevus

Development of a clinically dysplastic nevus

Development of a clinically dysplastic nevus

Microscopic (histologic) description
  • Familial or sporadic dysplastic nevi show the same features
  • Architectural changes:
    • Dysplastic nevus should not be diagnosed solely based on architectural atypia; cytologic atypia should also be present
      • Shouldering: the epidermal component extends at least 3 rete ridges beyond the lateral margin of the dermal component in compound nevi
      • Bridging: connection of the adjacent nests along elongated rete ridges
      • Lentiginous hyperplasia
      • Irregular nesting: nests show irregular sizes and shapes and are not confined to the tips of rete ridges
  • Cytological changes:
    • Increased nuclear size and hyperchromatic nuclei
    • Irregular nuclear membrane
    • Prominent nucleoli
    • Pleomorphism
    • Limited epidermal mitosis: melanoma should be suspected if there are multiple mitotic figures
    • Multivacuolated melanocytes in the dermal component
  • Cytologic atypia classified into mild, moderate or severe or simplified to low or high grade
  • Stromal changes:
    • Lamellar fibroplasia
    • Meyerson phenomenon: a subacute spongiotic dermatitis
    • Possible epidermal changes: acanthosis, focal parakeratosis, effacement of rete ridges, attenuation of the epidermis; however, the latter 2 features are typically absent in dysplastic nevus and are more characteristic of melanoma (Arch Dermatol Res 2022;314:159)
    • Epidermolytic hyperkeratosis may be present but not specific (Am J Dermatopathol 2002;24:23)
  • Nevus of special site: flexural, breast, genital and acral nevi can be clinically and histologically atypical and simulate features of a dysplastic nevus or melanoma (Mod Pathol 2006;19:S4)
    • The following criteria are not considered to be the typical features of special site nevi and dysplasia should be considered:
      • Nevus of genital skin:
        • Large and poorly circumscribed
        • Extensive shouldering
        • Significant epidermal pagetosis
        • Necrosis
        • Ulceration
        • Dermal mitosis
      • Nevus of flexural skin:
        • Cytologic atypia
        • Stromal alterations
      • Nevus of acral sites:
        • Acral nevi are often more cellular and are arranged in predominantly lentiginous pattern rather than nested patterns
        • Dysplastic nevi demonstrate uniform elongation and anastomosis of rete ridges
Microscopic (histologic) images

Contributed by Sepideh Nikki Asadbeigi, M.D., Aleodar Andea, M.D. and AFIP images
Dysplastic compound nevus with focally severe atypia

Focally severe atypia

Dermal - epidermal junctional nest bridging

Dermal - epidermal junctional nest bridging

Enlarged nevomelanocytes and dusty cytoplasm

Enlarged nevomelanocytes and dusty cytoplasm

Shouldering

Shouldering

Cytological atypia

Cytological atypia


Bridging and focal lentiginous spread of melanocytes

Bridging and focal lentiginous spread of melanocytes

Bridging

Bridging

Clark nevus

Clark nevus

Positive stains
Negative staining
Molecular / cytogenetics description
  • Mutation in BRAF is more common compared to benign nevus (62 - 81%)
  • RAS mutation is seen in congenital nevus and rarely in dysplastic nevus
  • Mutation / deletion of p16 tumor suppressor gene rarely in dysplastic nevus
  • Altered expression of p53
  • Increased microsatellite instability in dysplastic nevus; not seen in benign nevus
  • Some dysplastic nevi have deletion in p16 encoding chromosomal region 9p21
  • Usually diploid
  • 24% have high risk mucosal HPV by PCR (Br J Dermatol 2005;152:909)
  • Microarray analysis of 4 markers (ING4, Cul1, BRG1 and Bim) may distinguish melanoma from dysplastic nevi (PLoS One 2012;7:e45037)
Videos

Dysplastic nevus by Dr. Jerad Gardner

Compound Clark nevus

Dr. Clay Cockerell's approach to dysplastic nevi

Sample pathology report
  • Skin, left arm, shave biopsy:
    • Dysplastic compound nevus with severe atypia (see comment)
    • Comment: The process extends to lateral margins. A complete excision is recommended.
    • Microscopic description: Sections reveal junctional and dermal melanocytes arranged in irregular nests and single units. The lesion is poorly circumscribed and has some focal upward migration of melanocytes. The melanocytes show significant pleomorphism and hyperchromasia. Lamellar fibroplasia and a scattered lymphohistiocytic infiltrate are noted in the dermis.
Differential diagnosis
  • Banal nevus:
    • Minor architectural abnormalities can be present but cytological atypia is absent
  • Lentigo maligna:
    • Epidermal atrophy and effacement instead of epidermal hyperplasia
    • Dermis shows significant solar elastosis in lentigo maligna
  • Melanoma in situ, superficial spreading type:
    • Severely dysplastic nevi and early melanoma are difficult to distinguish and the diagnosis may be subjective
  • Recurrent nevus:
    • Scar of the previous biopsy or excision is present
    • Extension of the junctional component beyond the margins of scar may be a more concerning feature for melanoma
Board review style question #1
Which of the following favors a diagnosis of melanoma rather than dysplastic nevus?

  1. Bridging of the rete ridges
  2. Focal pagetosis of melanocytes
  3. Lamellar fibroplasia
  4. Mitotic activity in dermal melanocytes
Board review style answer #1
D. Mitotic activity in dermal melanocytes

Comment Here

Reference: Dysplastic nevus
Board review style question #2

Which mutation is more common in congenital nevi and is rarely seen in dysplastic nevi?

  1. BRAF V600E
  2. GNAQ
  3. P53
  4. RAS
Board review style answer #2
D. RAS

Comment Here

Reference: Dysplastic nevus
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