Skin melanocytic tumor

Congenital nevi and associated neoplasms

Congenital nevus


Editorial Board Member: Viktoryia Kozlouskaya, M.D., Ph.D.
Anila Chughtai, M.B.B.S.
Saba Anjum, M.B.B.S.

Last author update: 18 January 2023
Last staff update: 18 January 2023

Copyright: 2003-2024, PathologyOutlines.com, Inc.

PubMed Search: Congenital nevus skin

Anila Chughtai, M.B.B.S.
Saba Anjum, M.B.B.S.
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Cite this page: Chughtai A, Anjum S. Congenital nevus. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumormelanocyticmelanomacongenital.html. Accessed March 29th, 2024.
Definition / general
Essential features
Terminology
ICD coding
  • ICD-10: D22.30 - melanocytic nevi of unspecified part of face
Epidemiology
Sites
  • Trunk and legs, followed by head and neck, feet and hands
  • Can be multiple
  • Can have satellite lesions with large / giant lesions
Pathophysiology
Etiology
  • No known etiology
Clinical features
Diagnosis
  • Clinical presentation and histological examination is diagnostic
Laboratory
  • Usually not required
Prognostic factors
Case reports
Treatment
Clinical images

Contributed by Mark R. Wick, M.D.
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Breast skin



Images hosted on other servers:
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10 year old girl

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Dermoscopically typified by a globular pattern

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Papillomatous surface

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Verrucous surface and hair

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Giant CMN covering 20% of the total body surface area

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Newborn with giant hairy congenital nevus


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Ulcerated nodule within scalp

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Reticular pattern and regular globules

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Globular pattern and patchy network

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Haloed globules

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Target network and target globules

Gross description
Gross images

Contributed by Koteeswaran Govindaswamy, M.D. (Case #383)
Partial black discoloration

Partial black discoloration

Microscopic (histologic) description
  • Diffuse melanocytic proliferation in dermis with extension into subcutaneous fat
  • Grenz zone is identified between epidermis and melanocytes
  • Nevus cells encircle and extend to walls of dermal appendages, perineural space and blood vessels, and can dissect through collagen bundles
  • Variable pigmentation and focal neurotization may be present
  • Sparse mitotic activity
  • Neonates / young children can have any of these worrisome features: cytological atypia, increased mitotic activity, large junctional nests and pagetoid spread
  • Proliferation nodules in CMN
    • Large epithelioid melanocytes with mild nuclear pleomorphism
    • Mitoses are typically rare and do not exceed 1 mitosis/mm2
    • No abnormal mitosis or necrosis
    • Remain stable for a prolonged period of time and may regress spontaneously
  • References: Elder: Lever's Histopathology of the Skin, 11th Edition, 2014, Calonje: McKee's Pathology of the Skin, 5th Edition, 2019
Microscopic (histologic) images

Contributed by Anila Chughtai, M.B.B.S.
Dermal melanocytic proliferation Dermal melanocytic proliferation

Dermal melanocytic proliferation

Grenz zone

Grenz zone

Melanocytes dissecting collagen bands Melanocytes dissecting collagen bands

Melanocytes dissecting collagen bands


Melanocytes centered on pilosebaceous units Melanocytes centered on pilosebaceous units

Melanocytes centered on pilosebaceous units

Melanocytes involve arrector pili muscle

Melanocytes involve arrector pili muscle

Melanocytes centered on eccrine duct

Melanocytes centered on eccrine duct

Variable pigmentation

Variable pigmentation

Molecular / cytogenetics description
Sample pathology report
  • Pigmented skin lesion at scalp, excision:
    • Congenital melanocytic nevus (see comment)
    • Comment: Benign lesion with excellent prognosis.
    • Microscopic description: A dermal based proliferation of melanocytes arranged in small nests and cords, dissecting through dermal collagen bundles. A grenz zone is identified between epidermis and melanocytes. The melanocytes are bland with variable amount of melanin granules. The melanocytes ensheath pilosebaceous units and extend into arrector pili muscle. The lesion shows maturation at depth of the lesion. No evidence of cellular atypia, frequent mitoses or necrosis is found. The margins are clear.
Differential diagnosis
Board review style question #1
Congenital melanocytic nevi commonly harbor which of the following molecular alterations?

  1. ALK
  2. BRAF
  3. KRAS
  4. NRAS
  5. p16
Board review style answer #1
D. NRAS

Comment Here

Reference: Congenital nevus
Board review style question #2

Which prominent histological feature of congenital melanocytic nevi is shown in the microscopic image above?

  1. Involvement of dermal appendages
  2. Junctional nests of melanocytes
  3. Melanocytes dissecting through collagen bundle
  4. Pagetoid spread of melanocytes to epidermis
  5. Prominent nesting pattern
Board review style answer #2
A. Involvement of dermal appendages

Comment Here

Reference: Congenital nevus
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