Benign tumors
Atypical melanocytic nevi of genital type

Author: Sarah Strickland, M.D. (see Authors page)
Editor: Carlos Parra-Herran, M.D.

Revised: 4 August 2016, last major update July 2016

Copyright: (c) 2002-2016,, Inc.

PubMed Search: Atypical melanocytic nevi of genital type

Cite this page: Atypical melanocytic nevi of the genital type. website. Accessed October 23rd, 2016.
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
Micro 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
Micro Images

Images hosted on other servers:

Large and well circumscribed melanocytic lesion

Atypical genital nevi

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”

Pigmented lesion on the mons pubis of a 17 year old girl

Figures 1 - 4: Atypical genital nevus

Images hosted on Nature servers:

Genital pattern 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