Nevus (plural nevi) is a nonspecific medical term for a visible, circumscribed, chronic lesion of the skin or

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

. The term originates from ''nævus'', which is Latin for "birthmark"; however, a nevus can be either congenital (present at birth) or acquired. Common terms, including mole, birthmark, and beauty mark, are used to describe nevi, but these terms do not distinguish specific types of nevi from one another.

Classification

The term ''nevus'' is applied to a number of conditions caused by

neoplasias A neoplasm () is a type of abnormal and excessive growth of tissue (biology), tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tiss ...

and

hyperplasia Hyperplasia (from ancient Greek ὑπέρ ''huper'' 'over' + πλάσις ''plasis'' 'formation'), or hypergenesis, is an enlargement of an organ or tissue caused by an increase in the amount of organic tissue that results from cell proliferati ...

s of

melanocyte Melanocytes are melanin-producing neural crest-derived cells located in the bottom layer (the stratum basale) of the skin's epidermis, the middle layer of the eye (the uvea), the inner ear, vaginal epithelium, meninges, bones, and heart. ...

s, as well as a number of pigmentation disorders, both hypermelanotic (containing increased melanin, the pigment responsible for skin color) and hypomelanotic (containing decreased melanin). Suspicious skin moles which are multi-colored or pink may be a finding in skin cancer.

Increased melanin

Usually acquired

* Melanocytic nevus ** Melanocytic nevi can be categorized based on the location of melanocytic cells *** Junctional:

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...

*** Intradermal:

dermis The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...

*** 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. * Becker's nevus * Blue nevus (rarely congenital): A classic blue nevus is usually smaller than 1 cm, flat, and blue-black in color. * Hori's nevus *

Nevus spilus Nevus spilus, also known as speckled lentiginous nevus, is a light brown or tan birth mark, speckled with small, dark spots or small bumps. If it occurs in a segmental pattern then it is sometimes referred to as a Zosteriform speckled lentiginous ...

(speckled lentiginous nevus): This lesion includes dark speckles within a tan-brown background. * 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. This categorization is important because large congenital melanocytic nevi are associated with an increased risk of

melanoma Melanoma, also redundantly known as malignant melanoma, is a type of skin cancer that develops from the pigment-producing cells known as melanocytes. Melanomas typically occur in the skin, but may rarely occur in the mouth, intestines, or eye ( ...

, a serious type of skin cancer. *** Small: <1.5 cm *** Medium: 1.5–19.9 cm *** Large: ≥ 20 cm * Nevus of Ito * Nevus of Ota File:Conjunctival nevus.jpg, Conjunctival nevus of a 32-year-old male File:Micrograph of an intradermal melanocytic nevus.jpg, Micrograph of an intradermal melanocytic nevus File:Normal mole (1).jpg, Acquired melanocytic nevi File:Dysplastic nevi (4).jpg, Atypical nevus File:Becker's nevus of shoulder.JPG, Becker's nevus File:Blue Nevus.jpg, Blue nevus File:Naevus-spilus.jpg,

File:Spitz nevus.jpg, Spitz nevus File:Congenital nevus from CDC.jpg, Congenital melanocytic nevus File:Nevus of Ota Before IBRITE C.jpg, Nevus of Ota File:Compound nevus left buttock.jpg, Compound nevus, left buttock

Decreased melanin

Acquired

* Nevus anemicus

Congenital

* Nevus depigmentosus File:Nevus anemicus.jpg, Nevus anemicus File: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, connective tissue, and vascular malformations.

Epidermal nevi

These nevi represent excess growth of specific cells types found in the skin, including those that make up oil and sweat glands. *

Verrucous epidermal nevus Verrucous (appearing like a wart or "verruca") can refer to: * Verrucous carcinoma * Verrucous lupus erythematosus * Proliferative verrucous leukoplakia * Verrucous perforating collagenoma * Verrucous cyst * Verrucous vascular malformation * Unil ...

* Nevus sebaceous *

Nevus comedonicus '' Nevus comedonicus'' (also known as a comedo nevus) is characterized by closely arranged, grouped, often linear, slightly elevated papules that have at their center keratinous plugs resembling comedones.James, William; Berger, Timothy; Elston, Dir ...

Eccrine nevus An eccrine nevus is an extremely rare cutaneous condition that, histologically, is characterized by an increase in size or number of eccrine Merocrine (or eccrine) is a term used to classify exocrine glands and their secretions in the study of h ...

Apocrine nevus An Apocrine nevus is an extremely rare cutaneous condition that is composed of hyperplastic mature apocrine glands.Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McGraw-Hill. . See also * Eccrine nevus * ...

Connective tissue nevi

Connective tissue nevi represent abnormalities of

collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...

in the dermis, the deep layer of the skin. * Collagenoma * Elastoma

Vascular nevi

These nevi represent excess growth of blood vessels, including capillaries. * Nevus simplex (

nevus flammeus nuchae Naevus flammeus nuchae, or colloquially stork bite, is a congenital capillary malformation present in newborns. It is a common type of birthmark in a newborn. Prevalence and symptoms Stork bites occur in a significant number of newborns, with est ...

), also known as a ''stork bite'' or ''salmon patch''. File:NaevusSebaceus res.jpg, Nevus sebaceous File:Nevus flammeus nuchae ("stork bite" "Storchenbiss").JPG, Nevus flammeus nuchae

Intramucosal nevi

An ''intramucosal nevus'' is a nevus within the

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. Intramucosal nevi account for 64% of all reported case of oral nevi.

Diagnosis

Pie chart of incidence and malignancy of pigmented skin lesions

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. 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. In addition to histopathological examination, some lesions may also warrant additional tests to aid in diagnosis, including special stains,

immunohistochemistry Immunohistochemistry (IHC) is the most common application of immunostaining. It involves the process of selectively identifying antigens (proteins) in cells of a tissue section by exploiting the principle of antibodies binding specifically to an ...

, and electron microscopy. Typically, the nevi that exist since childhood are harmless. Image:Dermatoscope.jpg, A modern polarized dermatoscope Image:Dermatoscope1.JPG, A dermatoscope

Differential diagnoses

Hypermelanotic nevi must be differentiated from other types of pigmented skin lesions, including: * Lentigo simplex * Solar lentigo *

Café au lait macule A coffeehouse, coffee shop, or café is an establishment that primarily serves coffee of various types, notably espresso, latte, and cappuccino. Some coffeehouses may serve cold drinks, such as iced coffee and iced tea, as well as other no ...

* Ink-spot lentigo * Mucosal melanotic macule * Mongolian spot (dermal melanocytosis) File:CALSpot.jpg, Cafe au lait File:Mongolianspotphoto.jpg, Mongolian spot

Management

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

Observation

Destruction

* Chemical peels * Cryotherapy * Dermabrasion * Electrodessication *

Laser ablation Laser ablation or photoablation (also called laser blasting) is the process of removing material from a solid (or occasionally liquid) surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser ...

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.

Syndromes

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

Basal cell nevus syndrome Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nece ...

Blue rubber bleb nevus syndrome Blue rubber bleb nevus syndrome is a rare disorder that consists mainly of abnormal blood vessels affecting the skin or internal organs – usually the gastrointestinal tract. The disease is characterized by the presence of fluid-filled blisters ...

* Dysplastic nevus syndrome * Epidermal nevus syndrome * Linear nevus sebaceous syndrome

Etymology

A naevus may also be spelled nevus. The plural is nevi or naevi. The word is from ''nævus'', Latin for " birthmark" and is correctly pronounced Nye-voos.

References

External links

{{Authority control Dermatologic terminology Disturbances of human pigmentation Melanoma