Vulva, vagina & female urethra

Melanocytic lesions

Atypical melanocytic nevi of the genital type

Topic Completed: 1 July 2016

Minor changes: 2 February 2021

Copyright: 2002-2021,, Inc.

PubMed Search: Atypical melanocytic nevi of genital type

Sarah Strickland, M.D.
Carlos Parra-Herran, M.D.
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Cite this page: Strickland S. Atypical melanocytic nevi of the genital type. website. Accessed October 16th, 2021.
Essential features
  • Considered a nevus of special site
  • Atypical histologic features but benign behavior
  • Most commonly on labia majora, labia minora and clitoris
  • Also mons pubis and perineum
  • Hair bearing skin or mucosa
  • Occurs rarely on male genitalia
Clinical features
  • Usually does not recur following excision; only one case of local recurrence reported (Am J Surg Pathol 2008;32:51)
  • No documented metastases
  • Local excision
Clinical images

Images hosted on other servers:

Figure 3: Irregular dots on the periphery of the lesion

Figure 1: Photomicrograph of pigmented lesion

Gross description
Microscopic (histologic) description
  • Three histologic patterns originally described: (Hum Pathol 1998;29:S1)
    • Nested pattern - a predominance of variably sized but typically large, often oval nests, oriented perpendicular or parallel to the dermal-epidermal junction
    • Dyshesive nested pattern - nearly contiguous dyshesive nests forming a band that separates the epidermis from the mature dermal melanocytes
    • Crowded pattern - closely apposed ill defined nests and single cells obscuring the dermal epidermal junction

  • Junctional melanocytic proliferation composed of large, variably sized nests with prominent retraction artifact or cellular dyscohesion
    • Nests may be perpendicular or parallel to epidermal surface
    • Melanocytic cytologic atypia ranging from mild to severe
    • Focal pagetoid spread, most often centrally located
    • Common to see focal lentiginous melanocyte proliferation
    • Large underlying "mushroom shaped" dermal component with maturation
    • Adnexal involvement in up to 46%
    • Dermal mitoses uncommon but may be present: up to two per tissue section
    • Lymphocytic infiltrate inconspicuous
    • May see giant cells
    • Coarse melanin pigment and melanin incontinence
    • Nondescript stromal pattern / stromal fibrosis
Microscopic (histologic) images

Images hosted on other servers:

Melanocytic nests are
well delineated; arranged
as oval and somewhat
irregular masses

Large and uniform cells with prominent nucleoli

Nests of nevus cells arranged in a form known as "jigsaw puzzle"

Figures 1 - 4: Atypical genital nevus

Molecular / cytogenetics description
Differential diagnosis
  • Dysplastic nevus (DN):
    • More pronounced lentiginous proliferation of single cells
    • Smaller nests along elongated rete ridges
    • More pronounced shoulder component
    • Contains eosinophilic fibroplasia and lamellar fibroplasia (whereas atypical melanocytic nevus of genital type most often has a nondescript pattern of dermal fibrosis)
    • Increased lymphocytic infiltrate and vascular ectasia
  • Melanoma:
    • Primarily postmenopausal women
    • Lacks symmetry
    • Lacks maturation
    • Greater cytologic atypia
    • Increased dermal mitoses/atypical mitoses
    • Pagetoid spread of melanocytes more pronounced
    • Plaque-like lymphocytic infiltrate (if radial phase melanoma)
    • Diffuse eosinophilic fibrosis with angiogenesis
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