Skin melanocytic tumor
Nevi
Congenital nevus


Minor changes: 15 July 2021

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PubMed Search: Melanoma[TI] giant congenital nevus

Christopher S. Hale, M.D.
Nat Pernick, M.D.
Page views in 2020: 147
Page views in 2021 to date: 158
Cite this page: Hale C, Pernick N. Congenital nevus. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumormelanocyticmelanomacongenital.html. Accessed July 25th, 2021.
Giant congenital nevus
Definition / general

Terminology
  • Also called giant pigmented nevus or giant hairy nevus

Epidemiology
  • 1 in 500,000 live births (Br J Dermatol 1981;104:307)
  • ~2.5% risk of malignant transformation, usually before adolescence (Br J Dermatol 2006;155:1)
    • May give rise to cutaneous or CNS melanoma or related neuroectodermal tumors (malignant peripheral nerve sheath tumor, cutaneous malignant melanotic neurocristic tumor, rhabdomyosarcoma, liposarcoma)
  • May contain pseudotumoral proliferative nodules that ulcerate (J Cutan Pathol 2010;37:764)
  • May have satellite nevi, including within mucosal membranes
  • Truncal nevi may develop symptomatic neurocutaneous melanosis (meningeal or cerebral melanosis), lethal in 1/3 (J Am Acad Dermatol 2006;54:767)

Sites
  • Dermatomal, "bathing suit" or "garment" configuration; may involve entire scalp, extremity, most of trunk or placenta
  • Scalp lesions are often in thickened folds of skin resembling cerebrum, may involute in first 2 years of life (J Am Acad Dermatol 2008;58:508)

Case reports

Treatment

Clinical images

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Newborn with giant hairy congenital nevus

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Ulcerated nodule within scalp



Microscopic (histologic) description
  • Similar to congenital nevus
  • Deeper nevus cells may be E-cadherin negative, contributing to their motility (J Dermatol Sci 2008;52:21)

Microscopic (histologic) images

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Proliferation of melanocytes along hair follicle

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Melanocytes are uniform in large ulcerated nodule



Molecular / cytogenetics description
Nevus with features of congenital onset
Definition / general
  • Most rigidly definition is nevi present at birth
  • Disagreement regarding whether nevi presenting very early in life but not at birth can be considered congenital (Acta Derm Venereol 2012;92:586)
  • In practice, nevi often labeled congenital if they have congenital features of melanocytes clustered around follicles, adnexae, nerves and between collagen fibers at base of lesion
  • References: eMedicine, J Am Acad Dermatol 2012;67:495.e1

Terminology
  • Agminate / agminated nevus: nevi that are clustered and may be confined to a developmental segment (J Invest Dermatol 2011;131:788)
  • Nevus spilus / speckled lentiginous nevus: common type of agminate nevus with multiple pigmented macules or papules within a pigmented patch (Cutis 2007;80:465)
  • Neuronevus: compound nevi with prominent neural features, Masson's neuronevus (cellular blue nevus with neural / schwannian differentiation) or congenital nevus with prominent neural features
  • Giant congenital nevus: see above

Epidemiology

Clinical features

Case reports

Treatment

Dermoscopy

Clinical images

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



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Reticular pattern and regular globules

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Globular pattern and patchy network

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Haloed globules (3)

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Target network and target globules (4 and 5)



Gross images

Case #383

Partial black discoloration



Microscopic (histologic) description
  • Tends to involve reticular dermis, subcutis, skin adnexa, arrector pili muscles and nerves with single cell permeation of collagen
  • Also neural differentiation with Wagner-Meissner-like corpuscles
  • Frequent proliferative nodules
  • Lesions of infants may have pagetoid melanocytic proliferation
  • Proliferative nodules:
    • Dermal nodules of large epithelioid or spindled melanocytes that merge with surrounding nevus cells
    • Often prominent nucleoli, cellular areas, focal hemorrhage and ulceration but no necrosis, no destructive growth, minimal inflammation and 0 - 4 mitotic figures/10 HPF
    • Lesions mature and regress over time

Microscopic (histologic) images

Case #383



Various images



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Symmetrical broad proliferation of melanocytes
in papillary and reticular dermis with maturation,
splaying between collagen bundles, permeation of
muscles of hair erection, blood vessels, adnexa

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Deep congenital nevus



Molecular / cytogenetic description
  • Lesions present at birth usually have NRAS but not BRAF mutations
  • Lesions with congenital type histologic features but not present at birth more commonly have BRAF but not NRAS mutations (J Invest Dermatol 2007;127:179)
  • Germline Melanocortin-1-Receptor (MC1R) genotype is associated with severity of cutaneous phenotype in congenital melanocytic nevi (J Invest Dermatol 2012;132:2026)

Differential diagnosis
Congenital nevus (pending)
[Pending]
Melanoma arising in a giant congenital nevus (pending)
[Pending]
Proliferative nodule (pending)
[Pending]
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