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Melanoma variantDiagnostic pitfallICD-10 C43.x

Naevoid melanoma

Naevoid melanoma · nevoid melanoma · melanoma with naevoid features

Naevoid melanoma is a rare melanoma variant (~1-2% of melanomas) characterised by clinical and histological resemblance to a benign acquired naevus, making it a major diagnostic pitfall. The diagnosis requires careful pathology review for atypia, mitoses, deep dermal mitoses, expansile / sheet-like growth and absent maturation. Behaviour is similar to conventional melanoma stage-for-stage. Recognition prevents under-diagnosis of stage III / IV disease that may otherwise present as enlarging "naevi".

CurrentLast reviewed 16 May 2026

Clinical features

  • Domed papular or nodular pigmented lesion; symmetric appearance; well-circumscribed.
  • Brown / pink; minimal atypia clinically.
  • 2-15 mm diameter.
  • Sites: trunk, limbs, head & neck.
  • Adults; less age-restricted than conventional melanoma.
  • History may include slow growth, changes in size / colour, or asymptomatic.
  • May arise within a pre-existing naevus.

Pathology

  • Architectural appearance resembles benign compound or intradermal naevus:
    • Symmetric, well-circumscribed.
    • Nested arrangement.
    • Subtle confluence.
  • Diagnostic features identifying malignancy:
    • Atypia: nuclear pleomorphism, hyperchromasia, prominent nucleoli.
    • Mitoses: ≥1 / mm²; deep dermal mitoses particularly diagnostic.
    • Lack of maturation: cells retain size and chromatin pattern at the base.
    • Expansile growth.
    • Sheet-like architecture without maturation.
    • Lymphovascular invasion / perineural invasion.
  • IHC: Ki-67 elevated; HMB-45 maintained in deep dermis (cf naevi where lost); p16 reduced; PRAME positive (supports melanoma).
  • Molecular: BRAF / NRAS / TERT promoter mutations.

Differentials

  • Compound / intradermal melanocytic naevus — benign; maturation; no atypia / mitoses.
  • Dermal Spitz naevus — Kamino bodies; HRAS mutation; no atypia.
  • Atypical Spitz tumour.
  • Combined naevus.
  • BAP1-inactivated melanocytic tumour.
  • Cellular blue naevus.
  • Spitzoid melanoma.
  • Other naevoid melanocytic neoplasm.

Workup and management

  • Excisional biopsy for any clinically uncertain lesion with margin 1-2 mm.
  • Dermatopathology:
    • Specialist dermatopathologist review.
    • IHC: HMB-45, Melan-A, S100, SOX10, Ki-67, PRAME, p16.
    • Molecular: BRAF V600 (especially in stage III / IV).
    • FISH / CGH if histology equivocal — gains of 6p25, losses of 6q23 / 9p21 support melanoma.
  • Staging: AJCC 8 (Breslow, ulceration, mitotic rate); SLNB consideration based on standard NICE NG14 criteria.
  • Definitive management: wide local excision and SLNB per standard melanoma pathway.
  • Follow-up: standard surveillance per stage.
  • Counsel: same prognosis as stage-matched conventional melanoma; behaviour not different.

Practical points

  • Have a high index of suspicion for "atypical naevus" in adults with slow growth.
  • Always send to specialist dermatopathology; second opinion in equivocal cases.
  • Use of PRAME IHC and BRAF molecular testing has improved diagnostic precision.
  • Document a chain of pathological reasoning in MDT minutes.
  • Avoid "atypical naevus, not for excision" diagnosis in adult lesions with growth — full excision permits definitive diagnosis.

References

  1. Zembowicz A et al. Nevoid melanoma. Mod Pathol. 2006;19(Suppl 2):S5-S15.
  2. McNutt NS, Mihm MC. Naevoid melanoma. Am J Surg Pathol. 1993;17:931-941.
  3. Lezcano C et al. PRAME expression in melanocytic tumors. Am J Surg Pathol. 2018;42:1456-1465.
  4. NICE NG14. Melanoma: assessment and management. London: NICE; 2015 (last updated 27 July 2022).
  5. NICE NG14. Melanoma: assessment and management. London: NICE; 2022.

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