Common Acquired Melanocytic Nevi

Common Acquired Melanocytic Nevi

Christine J. Ko, MD

This junctional melanocytic nevus is an oval macule of even, light brown pigment. There is overall symmetry with a smooth border; the size was measured to be 2 × 1 mm.

This junctional melanocytic nevus shows nests at the tips and sides of rete ridges. The presence of pigmented parakeratosis and pigment incontinence image likely corresponds to a dark color clinically.



  • Benign melanocytic nevus, junctional melanocytic nevus, compound melanocytic nevus, intradermal melanocytic nevus, common mole, common melanocytic nevus, nevocellular nevus


Exact Etiology Unknown

  • Believed by some to arise from intraepidermal melanocytes

  • Others suggest that melanocytic nevi arise from nerves or pluripotential cells

Tumor vs. Hamartoma?

  • Still debated

  • Evidence for tumor

    • Studies showing that some nevi are clonal

    • Growth advantage of nevus cells over epidermal, dendritic melanocytes in cell culture

    • Similar expression of different markers by nevi and malignant melanoma

    • Presence of mutations in BRAF oncogene in majority of nevi

  • Evidence for hamartoma

    • Other proliferative elements: Epidermal, follicular, connective tissue

    • Studies showing that some nevi are polyclonal



  • Incidence

    • Number of acquired nevi

      • Increases with age up to 3rd decade

      • May be related to familial predisposition

      • Sun exposure in childhood also linked to development of nevi

      • More common in lighter skinned individuals

  • Age

    • Not present at birth

    • Majority develop in adolescence

    • Density of nevi generally decreases after 4th decade


  • Junctional lesions

    • Flat to minimally raised macule/very thin papule

    • Generally < 6 mm, but may be larger

    • Color often a variation of brown

  • Compound lesions

    • Slightly raised papule

    • Variable color (brown, flesh-colored, pink)

    • May contain hair

  • Intradermal lesions

    • Papule, may be pedunculated

    • Variable color (brown, flesh-colored, pink)

    • May contain hair

Natural History

  • Abtropfung hypothesis of Unna

    • Melanocytes are initially junctional

    • With chronologic time (aging), melanocytes “drop off” into dermis, creating compound melanocytic lesions

    • With more time, the junctional melanocytes have all “dropped off,” creating intradermal melanocytic lesions

    • Intradermal melanocytic lesions may eventually “shed” or become acrochordons

      • Degenerative changes include balloon cell change and fatty change

  • Alternative hypothesis

    • Nevi begin in the dermis

  • Not all melanocytic nevi display progressive changes; some arrest at a given stage indefinitely


  • Not necessary

  • Conservative removal (e.g., shave removal) generally sufficient

    • Residual dark pigment may remain

    • Pigment may recur irregularly within scar (recurrent nevus)


  • Benign


Histologic Features

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Common Acquired Melanocytic Nevi
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