Nevus

Nevus (Template:Plural abbr) is a nonspecific medical term for a visible, circumscribed, chronic lesion of the skin or mucosa.<ref>Template:Cite journal</ref> The term originates from Template:Wikt-lang, which is Latin for "birthmark"; however, a nevus can be either congenital (present at birth) or acquired. Common terms (mole, birthmark, beauty mark, etc.) are used to describe nevi, but these terms do not distinguish specific types of nevi from one another. Template:TOC limit

Classification

The term nevus is applied to a number of conditions caused by neoplasias and hyperplasias of melanocytes,<ref name=":0">Template:Cite book</ref> as well as a number of pigmentation disorders, both hypermelanotic (containing increased melanin, the pigment responsible for skin color) and hypomelanotic (containing decreased melanin).<ref>Template:Cite book</ref> Suspicious skin moles which are multi-colored or pink may be a finding in skin cancer.<ref name="Ba2012">Template:Cite book</ref>

Increased melanin

Usually acquired

• Melanocytic nevus
  • Melanocytic nevi can be categorized based on the location of melanocytic cells<ref name=":0" />
    • Junctional: epidermis
    • Intradermal: dermis
    • Compound: epidermis and dermis
• Atypical (dysplastic) nevus: This type of nevus must be diagnosed based on histological features. Clinically, atypical nevi are characterized by variable pigmentation and irregular borders.<ref>Template:Cite book</ref>
• Becker's nevus
• Blue nevus (rarely congenital): A classic blue nevus is usually smaller than 1 cm, flat, and blue-black in color.<ref name=":1" />
• Hori's nevus
• Nevus spilus (speckled lentiginous nevus): This lesion includes dark speckles within a tan-brown background.<ref name=":2" />
• Pigmented spindle cell nevus
• Spitz nevus
• Zosteriform lentiginous nevus

Usually congenital

• Congenital melanocytic nevus
  • These nevi are often categorized based on size, however, the lesions usually grow in proportion to the body over time, so the category may change over an individual's life.<ref name=":0" /> This categorization is important because large congenital melanocytic nevi are associated with an increased risk of melanoma, a serious type of skin cancer.<ref name=":0" />
    • Small: <1.5 cm<ref name=":0" />
    • Medium: 1.5–19.9 cm<ref name=":0" />
    • Large: ≥ 20 cm<ref name=":0" />
• Nevus of Ito
• Nevus of Ota

• Conjunctival nevus.jpg

  Conjunctival nevus of a 32-year-old male

• Micrograph of an intradermal melanocytic nevus.jpg

  Micrograph of an intradermal melanocytic nevus

• Normal mole (1).jpg

  Acquired melanocytic nevi

• Dysplastic nevi (4).jpg

  Atypical nevus

• Becker's nevus of shoulder.JPG

  Becker's nevus

• Blue Nevus.jpg

  Blue nevus

• Naevus-spilus.jpg

  Nevus spilus

• Spitz nevus.jpg

  Spitz nevus

• Congenital nevus from CDC.jpg

  Congenital melanocytic nevus

• Nevus of Ota Before IBRITE C.jpg

  Nevus of Ota

• Compound nevus left buttock.jpg

  Compound nevus, left buttock

Decreased melanin

Acquired

• Nevus anemicus

Congenital

• Nevus depigmentosus

• Nevus anemicus.jpg

  Nevus anemicus

• Nevus Depigmentosus.jpg

  Nevus depigmentosus

Additional types of nevi do not involve disorders of pigmentation or melanocytes. These additional nevi represent hamartomatous proliferations of the epithelium,<ref name=":3">Template:Cite book</ref> connective tissue,<ref name=":4">Template:Cite book</ref> and vascular malformations.<ref>Template:Cite book</ref>

Epidermal nevi

These nevi represent excess growth of specific cells types found in the skin, including those that make up oil and sweat glands.<ref name=":3" />

• Verrucous epidermal nevus
• Nevus sebaceous
• Nevus comedonicus
• Eccrine nevus
• Apocrine nevus

Connective tissue nevi

Connective tissue nevi represent abnormalities of collagen in the dermis, the deep layer of the skin.<ref name=":4" />

• Collagenoma
• Elastoma

Vascular nevi

These nevi represent excess growth of blood vessels, including capillaries.<ref>Template:Cite book</ref>

• Nevus simplex (nevus flammeus nuchae), also known as a stork bite or salmon patch.

• NaevusSebaceus res.jpg

  Nevus sebaceous

• Nevus flammeus nuchae ("stork bite" "Storchenbiss").JPG

  Nevus flammeus nuchae

Intramucosal nevi

An intramucosal nevus is a nevus within the mucosa as found in for example the mouth and genital areas. In the mouth, they are found most frequently on the hard palate. They are typically light brown and dome-shaped.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Intramucosal nevi account for 64% of all reported case of oral nevi.<ref name="BuchnerMerrell2004">Template:Cite journal</ref>

Diagnosis

File:Pie chart of incidence and malignancy of pigmented skin lesions.png

Various differential diagnoses of pigmented skin lesions, by relative rates for biopsied lesions, and malignancy potential, including "nevus" at left and top.

Nevi are typically diagnosed clinically with the naked eye or using dermatoscopy. More advanced imaging tests are available for distinguishing melanocytic nevi from melanoma, including computerized dermoscopy and image analysis.<ref>Template:Cite journal</ref> The management of nevi depends on the type of nevus and the degree of diagnostic uncertainty. Some nevi are known to be benign, and may simply be monitored over time. Others may warrant more thorough examination and biopsy for histopathological examination (looking at a sample of skin under a microscope to detect unique cellular features). For example, a clinician may want to determine whether a pigmented nevus is a type of melanocytic nevus, dysplastic nevus, or melanoma as some of these skin lesions pose a risk for malignancy. The ABCDE criteria (asymmetry, border irregularity, color variegation, diameter > 6 mm, and evolution) are often used to distinguish nevi from melanomas in adults, while modified criteria (amelanosis, bleeding or bumps, uniform color, small diameter or de novo, and evolution) can be used when evaluating suspicious lesions in children.<ref>Template:Cite journal</ref> In addition to histopathological examination, some lesions may also warrant additional tests to aid in diagnosis, including special stains, immunohistochemistry, and electron microscopy.<ref>Template:Cite book</ref> Typically, the nevi that exist since childhood are harmless.

• Dermatoscope.jpg

  A modern polarized dermatoscope

• Dermatoscope1.JPG

  A dermatoscope

Differential diagnoses

Hypermelanotic nevi must be differentiated from other types of pigmented skin lesions, including:<ref name=":1">Template:Cite book</ref><ref name=":2">Template:Cite book</ref>

• Lentigo simplex
• Solar lentigo
• Café au lait macule
• Ink-spot lentigo
• Mucosal melanotic macule
• Mongolian spot (dermal melanocytosis)

• CALSpot.jpg

  Cafe au lait

• Mongolianspotphoto.jpg

  Mongolian spot

Management

File:Cryogun.jpg

Cryotherapy

The management of a nevus depends on the specific diagnosis, however, the options for treatment generally include the following modalities:

Destruction

• Chemical peels
• Cryotherapy
• Dermabrasion
• Electrodessication
• Laser ablation

Surgery

The decision to observe or treat a nevus may depend on a number of factors, including cosmetic concerns, irritative symptoms (e.g., pruritus), ulceration, infection, and concern for potential malignancy.<ref name=":0" />

Syndromes

The term nevus is included in the names of multiple dermatologic syndromes:

• Basal cell nevus syndrome
• Blue rubber bleb nevus syndrome
• Dysplastic nevus syndrome
• Epidermal nevus syndrome
• Linear nevus sebaceous syndrome

See also

• Skin lesion