Nevus

Nevi are congenital or acquired benign neoplasms of the skin that are classified as either melanocytic or epidermal. Melanocytic nevi (moles) are composed of pigment-producing nevus cells derived from melanocytes and can manifest in multiple forms (e.g., common acquired melanocytic nevus, atypical nevus, Spitz nevus). Epidermal nevi are cutaneous hamartomas caused by hyperplasia of the epidermis and/or adnexa that typically manifest at birth or during early childhood, and occur either as an isolated lesion (e.g., nevus sebaceous, inflammatory linear verrucous epidermal nevus, and Becker nevus) or with extracutaneous abnormalities (i.e., epidermal nevus syndrome). Careful history taking and skin examination are required to differentiate between the types of nevi. If there is concern for malignancy (e.g., ABCDE criteria, ugly duckling sign, clinical features of BCC) or Spitz nevus, a skin biopsy is necessary. Individuals with a suspected epidermal nevus syndrome require further evaluation and management by a specialist. All individuals with histologic confirmation of malignancy should be treated accordingly; see also “Treatment of BCC” and “Treatment of melanoma.” Otherwise, treatment is generally unnecessary unless desired for cosmetic reasons.

Congenital melanocytic nevus and congenital dermal melanocytosis are discussed elsewhere.

Overview ^[1][2]

• Melanocytic nevus (mole) is a benign cutaneous tumor composed of pigment-producing nevus cells derived from melanocytes.
• Histopathology: well-nested melanocytic proliferations at the dermal-epidermal junction

Congenital dermal melanocytosis is a birthmark that manifests as a painless, blue-gray, nonblanching, hyperpigmented macula of the sacral region, and typically disappears in childhood.

General management of melanocytic nevus ^[1][2]

• Melanocytic nevus is a clinical diagnosis based on:
  • Complete skin examination
  • Dermoscopy as needed
• Perform a full-thickness excisional biopsy if there is suspicion for:
  • Melanoma (i.e., ABCDE criteria and/or ugly duckling sign; see also “Diagnostics for melanoma”) ^[4][5]
  • Spitz nevus
• Specific management depends on the type of nevus.

• Definition: an acquired melanocytic nevus that arises from clusters of melanocytic nevus cells in the epidermis and dermis and manifests as a uniformly pigmented lesion ^[1][2]
• Epidemiology: common regardless of age, gender, or ethnicity
• Etiology
  • Genetics (parents with many moles)
  • Associated with light skin and red hair
  • Intense sun exposure during childhood
• Clinical features ^[2]
  • Most commonly on sun-exposed areas ^[1]
  • Uniform in color and shape
• Stages ^[1][2]
  • Junctional nevus
    • Uniformly brown-black macule with a flat smooth, hairless surface and well-demarcated border
    • Grows at the dermal-epidermal junction during childhood
  • Compound nevus
    • Uniformly brown-black, dome-shaped elevated papule or nodule with a smooth or verrucous surface; hair may be present
    • Arises from a junctional nevus and extends to the dermis after childhood
  • Dermal nevus
    • Uniformly brown-black, dome-shaped elevated nodule with a smooth or verrucous surface; can become fibrotic over time and hair may be present
    • Arises from a compound nevus in the dermis in adults
• Management ^[1][2]
  • See “General management of melanocytic nevus.”
  • Treatment usually not required unless the patient requests lesion removal for cosmetic reasons
• Prognosis: Transformation to melanoma is rare. ^[2]

Atypical nevus was previously known as dysplastic nevus. ^[4]

• Description: a benign melanocytic nevus that resembles melanoma and is a risk factor for developing melanoma ^[3][4]
• Epidemiology: 2–10% in White individuals
• Etiology
  • Genetics (parents with many moles)
  • Associated with light skin
  • Intense sun exposure during childhood
• Clinical features ^[3][4]
  • Typically on sun-exposed areas in light skin and non-sun-exposed areas in dark skin
  • Appearance is similar to the ABCDE criteria for melanoma:
    • Asymmetry
    • Irregular borders
    • Color variegation
    • Diameter > 5 mm ^[3]
• Management ^[4][5]
  • See “General management of melanocytic nevus.”
  • If melanoma is not currently suspected, monitor with periodic screening.
    • Modality: total body skin examination with dermoscopy and/or total body photography
    • Frequency: Consider every 3–12 months, depending on risk factors. ^[4][5]
  • Educate patients to self-monitor for concerning changes in existing nevi.
• Prevention
  • Minimize UV radiation exposure (e.g., with photoprotective measures). ^[4][5]
  • See also “Prevention of melanoma.”
• Prognosis
  • Lifetime risk of melanoma increases in proportion to the number of atypical nevi. ^[4]
  • Individuals with familial atypical multiple mole melanoma syndrome (FAMMM) have up to 100% lifetime risk of developing melanoma. ^[4]

• Description: a benign type of melanocytic nevus characterized by spindle cells and/or epithelioid cells ^[1][6]
• Epidemiology: most common during the first two decades of life ^[1]
• Etiology: unknown (associated with pregnancy and puberty)
• Histology: large epithelioid and spindle cells ^[1]
• Clinical features ^[1][6]
  • Rapidly growing solitary lesion
  • Located on the head, neck, or lower extremities
  • Small, symmetrical, dome-shaped well-circumscribed papule or nodule (< 1 cm in diameter), with a smooth surface ^[1]
  • Commonly pink-red; may also be tan, red-brown, or black
  • Atypical lesions manifest with features that resemble melanoma (i.e., ABCDE criteria, easy friability).
• Management ^[1][6]
  • Diagnosis is clinical, based on comprehensive skin examination and dermoscopy as needed.
  • Perform a full-thickness excisional biopsy for histopathological confirmation in all lesions. ^[1][7]

• Description: a benign type of melanocytic nevus that is a subtype of congenital melanocytic nevi ^[2][8]
• Epidemiology: prevalence of ∼ 2%
• Etiology
  • Not fully understood
  • Environmental and genetic influences possible
• Clinical features ^[2][8]
  • Appears at birth or during infancy as a light café-au-lait spot
  • Lesions can grow larger over months to years with the following features:
    • Irregular oval macule or patch (1–20 cm in diameter) that is hairless, flat, and brown ^[2]
    • Speckled with small, elevated black dots (1–3 mm in diameter) ^[2]
• Management ^[2]
  • See “General management of melanocytic nevus.”
  • Lesion removal or referral for laser therapy may be offered for cosmetic reasons if desired by the patient.
  • Advise patients and caregivers to monitor the lesion for ABCDE criteria for melanoma.

Overview

Epidermal nevus is a cutaneous hamartoma of the epidermis and/or skin adnexa (skin adnexal tumor); melanocytic nevus cells are not present. ^[1]

General management of epidermal nevus ^[1][2][9]

• Epidermal nevus is a clinical diagnosis based on:
  • Complete skin examination
  • Dermoscopy as needed
• Evaluate for epidermal nevus syndromes with a complete history (including birth and family history) and physical examination.
• Refer to a dermatologist in patients with:
  • Diagnostic uncertainty
  • Suspicion for epidermal nevus syndrome
• Specific management depends on the type of nevus.

• Definition: a common congenital epidermal nevus ^[9]
• Epidemiology: most commonly occurs at birth or during early childhood ^[2]
• Etiology: sporadic gene mutations ^[9]
• Clinical features ^[1][2][9]
  • Typically manifests as a single asymptomatic lesion
    • Most commonly seen on the scalp but may occur on the face, trunk, neck, or behind the ear
    • Appears as a smooth or cobblestone-like, linear or oval hairless plaque (0.5–9 cm in diameter) ^[2]
    • Becomes significantly more verrucous around puberty
    • Color varies (e.g., yellow-orange, pink)
  • Epidermal nevus syndrome (atypical manifestation): large lesion, centrofacial distribution, and extracutaneous symptoms
• Management ^[2][9]
  • See “General management of epidermal nevus.”
  • Consider surgical excision, especially if the lesion persists beyond puberty. ^[1][2]
• Prognosis: ∼ 20% of lesions that persist in individuals > 40 years of age develop into secondary neoplasms, e.g., basal cell carcinoma. ^[1][2]

• Definition: a type of epidermal nevus that manifests as an asymptomatic, pigmented hamartoma, often with hair growth ^[1][9]
• Epidemiology
  • Most commonly develops around puberty ^[9]
  • Sex: ♂ > ♀ ^[1]
• Etiology
  • ↑ Androgen receptors ^[9]
  • Exposure to sunlight
• Clinical features ^[1][9]
  • Located on trunk or upper extremities
  • Light brown macule or patch with a well-demarcated, irregular border ^[1]
  • Smooth and elevated verrucous surface
  • Often with hair growth
  • Epidermal nevus syndrome (atypical manifestation): lesion in combination with developmental abnormalities (e.g., musculoskeletal malformations of the chest and limbs)
• Management ^[1][9]
  • See “General management of epidermal nevus.”
  • Refer to a dermatologist for laser therapy if desired for cosmetic reasons.
• Prognosis: Malignancy is rare. ^[9]

• Description: a rare inflammatory type of epidermal nevus with an unknown genetic cause ^[9][10]
• Epidemiology: 1–3/1000 live births
• Etiology: sporadic, may be associated with other developmental abnormalities
• Clinical features ^[2][9]
  • Linear, erythematous, and scaly plaque with a verrucous surface
  • Most commonly appears on the extremities along Blaschko's lines
  • Pruritus
  • Chronic and intermittent inflammation
• Management ^[9]
  • See “General management of epidermal nevus.”
  • Refer to a dermatologist for treatment if desired for cosmetic reasons and/or to relieve symptoms.