Skin melanocytic tumor

Melanocytic tumors on acral skin and nail apparatus

Acral nevus



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PubMed Search: Acral nevus

Gerardo Cazzato, M.D.
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Cite this page: Cazzato G. Acral nevus. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumormelanocyticnevisitesacral.html. Accessed December 1st, 2022.
Definition / general
  • Melanocytic nevi on the skin of soles and palms, nail matrix or bed, knees and elbows
  • Nevi on acral skin are rarely precursors of melanoma (Dermatopathology (Basel) 2022;9:292)
Essential features
  • Melanocytic nevi on the skin of soles and palms, nail matrix or bed, knees and elbows
  • Rarely, acral nevi are precursors of melanoma
  • Dermoscopy plays a central role in the diagnosis of acral nevi
  • Histological findings can be typical or atypical
  • Dysplastic is a term that should not be used on the acral skin
Terminology
  • Atypical or acral lentiginous nevus; nevus of special sites; nail matrix nevus
ICD coding
Epidemiology
Sites
  • Palms, soles, fingernails > toenails
Clinical features
  • Usually small, dark brown or black lesions, with irregular but sharp margins
  • Most are flat and rarely (particularly on the volar skin) elevated
Diagnosis
  • Dermoscopy plays a crucial role in the diagnosis
  • Array of thin, parallel dark brown lines in a light brown background (J Dermatol 2011;38:25)
  • Maturation deep to melanocytes is the most strong indicative parameter of a benign acral nevus
Prognostic factors
Case reports
Treatment
  • Excision
Clinical images

Contributed by Lucia Lospalluti, M.D.

Small and dark brown lesion

Pigmented acral lesion

Pigmented acral nevus on a foot



Images hosted on other servers:
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Various patterns

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Transition pattern

Microscopic (histologic) description
  • About half of the cases are typical and without any peculiar aspects (so called typical features)
  • May be junctional, compound or intradermal
  • Small nests of epithelioid cells with inconspicuous nuclei at the junction and small, round melanocytes in the dermis
  • Lentiginous junctional pattern is more common than in nevi of nonacral sites (so called acral nevi with atypical features)
  • Often (61%) low level pagetoid, single cell migration into stratum spinosum, summarized by the acronym MANIAC (melanocytic acral nevus with intraepithelial ascent of cells) (Am J Surg Pathol 1995;19:792, Am J Dermatopathol 2000;22:556)
  • Pagetoid cells should not be atypical and should not be present beyond the center of the lesion
  • Possible columns of pigment present in the cornified layer, among the corneocytes
  • Nevus cells mature to lesional base
  • May have architectural disorder (J Cutan Pathol 2008;35:889)
  • Usually lesions do not seem well circumscribed (this phenomenon can also depend on the plane of the section)
Microscopic (histologic) images

Contributed by Gerardo Cazzato, M.D. and Angel Fernandez-Flores, M.D., Ph.D.

Poor circumscription

Nests of melanocytes

Pigmented nests of melanocytes

Missing Image

Acral nevus

Melanocytes of acral nevus

Pseudo dysplastic melanocytes

Sample pathology report
  • Skin, excision:
    • Acral nevus (see comment)
    • Comment: Compound melanocytic cutaneous nevus of congenital type in acral type skin (acral type nevus). Free margins.
Differential diagnosis
Board review style question #1

What is the most important clinical aid in the dermatopathological diagnosis of an acral nevus?

  1. Asymmetry
  2. Borders
  3. Color
  4. Dermoscopy
  5. Time of onset
Board review style answer #1
D. Dermoscopy is the most important clinical feature to help the dermatopathological diagnosis of acral nevi. A pattern with an array of thin, parallel, dark brown lines in a light brown background are characteristic of the lesion. Asymmetry (answer A), borders (answer B), color (answer C) and time of onset (answer E) are also important but in the second instance.

Comment Here

Reference: Acral nevus
Board review style question #2
In an acral nevus showing lively junctional activity, what is the diagnostic clue of benignity of the lesion?

  1. Asymmetry
  2. Localization
  3. Maturation deep to melanocytes
  4. Small nests of melanocytes at the junction
  5. Time of onset
Board review style answer #2
C. Maturation deep to melanocytes is the most histological parameter for the benignity of the lesion. Asymmetry (answer A) is a possibility for an acral nevus. Localization (answer B) is obvious but not an indicator of malignancy. Small nests of melanocytes at the junction (answer D) and time of onset (answer E) are common in an acral nevus without signs of malignancy.

Comment Here

Reference: Acral nevus
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