Melanocytic Naevi ("Moles") and Atypical Naevi

Melanocytic naevi are benign proliferations of melanocytes. The history aims to identify features concerning for malignant change (melanoma).

Onset & Evolution

• When first noticed? (Most common moles appear in childhood/early adulthood; new pigmented lesions after age 40 are more concerning.) Ask about any change in size, shape, colour, itch, pain, or bleeding (Evolution).

Melanoma Risk

• Number of moles (many, especially >50–100, increases risk). History of a "funny-looking" mole compared to others (ugly duckling sign).

Personal/Family History

• Previous melanoma, other skin cancers, or a first-degree relative with melanoma or Atypical Mole Syndrome (FAMMM).

History Specific to Skin of Colour (SOC):

• Melanoma is less common but often diagnosed later. The most concerning types are often on non–sun-exposed sites.

• Ask specifically about any changing dark spot on the palms, soles, or nail units.

• New or changing dark streak in a single nail (Longitudinal Melanonychia) is a high-risk sign.

Inspect the entire skin surface in good light, including the scalp, palms, soles, nails, and mucosae.

Typical Benign Melanocytic Naevus

• • Appearance: Well-circumscribed, symmetric macule or papule.

  • Colour: Uniform light-to-dark brown, or skin-coloured/pink.

  • Size: Usually <6 mm.

  • Types: Junctional (flat), Compound (slightly raised), or Dermal (soft, dome-shaped papule).

Atypical (Dysplastic) Naevus

• • Features: Often larger (>5–6 mm).

  • Borders: Ill-defined or irregular.

  • Colour: Colour variegation (multiple shades: tan, brown, reddish-brown).

  • Shape: May have a "fried-egg" appearance (raised centre with a macular pigmented rim).

  • Assessment: Assess all moles using the ABCDE criteria for melanoma: Asymmetry, Border irregularity, Colour variation, Diameter >6 mm, and Evolving.

Examination in Skin of Colour:

• • Naevi tend to be dark brown to black.

  • Pay close attention to the ugly duckling sign (a mole that looks different from the patient’s other moles).

  • Acral Sites: Any expanding dark patch or streak on palms, soles, or nails should be taken very seriously as it may mimic Acral Lentiginous Melanoma (ALM).

  • Nail Unit: Look for a single, broad, irregular, or changing longitudinal melanonychia (dark streak), especially if the pigment extends to the surrounding skin (Hutchinson’s sign).

Treatment is primarily risk management and determining when to excise a lesion.

1. Benign-Appearing Common Naevi

• No active treatment needed.

• Sun Protection: Advise Broad-spectrum SPF 30+ daily, protective clothing, and shade, especially for patients with many moles.

• Self-monitoring: Advise monthly self-skin checks, focusing on change (Evolution) and the ugly duckling sign.

2. Atypical / Dysplastic Naevi

• Indications for Biopsy / Excision:

  • Any lesion with concerning ABCDE features or signs of Evolution.

  • A new pigmented lesion in an adult, especially over 40.

  • Ugly duckling mole that doesn't fit the patient's pattern.

  • For SOC: Any changing acral lesion or a suspicious nail streak.

• Preferred Approach: Complete excision biopsy with narrow margins is preferred for suspicious flat lesions to allow the pathologist to fully assess the architecture and rule out melanoma.

• Follow-up: Patients with multiple atypical naevi or a strong family history require regular dermatology review (e.g., 4–12-monthly) and possibly total body photography.

3. Special Considerations in Skin of Colour

• Threshold to Biopsy: Maintain a lower threshold to biopsy evolving lesions, especially on acral (hands/feet) or mucosal sites, due to the higher mortality associated with late diagnosis of ALM.

• Education: Spend time educating patients to check their palms, soles, nails, and mucosa and to not assume their dark skin offers complete protection from skin cancer.

• Cosmetic Outcomes: Surgical scars and PIH/hypopigmentation can be more noticeable. When removing benign but cosmetically prominent moles, discuss this risk; however, safety (ruling out melanoma) must outweigh cosmetic concerns.

1. Skinsight – Atypical Nevus (Mole, Atypical)

2. StatPearls / NCBI Bookshelf – Atypical Mole (Wensley & Zito, 2023)

3. DermNet NZ – Melanocytic Naevus (Oakley, 2016)