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Nevus (plural nevi) is a nonspecific medical term for a visible, circumscribed, chronic
lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classif ...
of the
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...
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 i ...
. 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. 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 tissue, and persists ...
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 proliferatio ...
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 hear ...
s, as well as a number of pigmentation disorders, both hypermelanotic (containing increased
melanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...
, 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 Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC) ...
.


Increased melanin


Usually acquired

*
Melanocytic nevus A melanocytic nevus (also known as nevocytic nevus, nevus-cell nevus and commonly as a mole) is a type of melanocytic tumor that contains nevus cells. Some sources equate the term mole with "melanocytic nevus", but there are also sources that equa ...
** 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 rel ...
*** 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 ...
*** 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 Becker's nevus (also known as "Becker's melanosis", "Becker's pigmentary hamartoma", "nevoid melanosis", and "pigmented hairy epidermal nevus") is a benign skin disorder predominantly affecting males. The nevus can be present at birth, but more of ...
* Blue nevus (rarely congenital): A classic blue nevus is usually smaller than 1 cm, flat, and blue-black in color. *
Hori's nevus Hori's nevus (also known as "Acquired bilateral nevus of Ota-like macules") is a cutaneous condition characterized by multiple brown–gray to brown–blue macules, primarily in the malar region of the face. See also * Nevus of Ota * List of cut ...
*
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 lentiginou ...
(speckled lentiginous nevus): This lesion includes dark speckles within a tan-brown background. *
Pigmented spindle cell nevus A pigmented spindle cell nevus is a skin condition characterized by a dark brown to black macule or papule, usually less than 6 mm. It was characterized in 1975. See also * Partial unilateral lentiginosis * List of cutaneous conditions ...
*
Spitz nevus A Spitz nevus is a benign skin lesion. A type of melanocytic nevus, it affects the epidermis and dermis.LeBoit, PE, Burg G, Weedon D, Sarasin A. (Eds) World Health Organization Classification of Tumours: Pathology and Genetics of Skin Tumours. Lyo ...
* 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 Nevus of Ota is a hyperpigmentation that occurs on the face, most often appearing on the white of the eye. It also occurs on the forehead, nose, cheek, periorbital region, and temple. It was first reported by Masao Ōta of Japan in 1939. Cau ...
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 A melanocytic nevus (also known as nevocytic nevus, nevus-cell nevus and commonly as a mole) is a type of melanocytic tumor that contains nevus cells. Some sources equate the term mole with "melanocytic nevus", but there are also sources that equa ...
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,
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 lentiginou ...
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 Nevus anemicus is a congenital disorder characterized by macules of varying size and shape that are paler than the surrounding skin and cannot be made red by trauma, cold, or heat.James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Dis ...


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 * U ...
*
Nevus sebaceous Nevus sebaceus or sebaceous nevus (the first term is its Latin name, the second term is its name in English; also known as an "organoid nevus"James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatolog ...
*
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, Di ...
*
Eccrine nevus An eccrine nevus is an extremely rare cutaneous condition that, histologically, is characterized by an increase in size or number of eccrine secretory coils.Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McG ...
*
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 whol ...
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 es ...
), 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
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 i ...
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

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 A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a dise ...
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 ant ...
, 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 Lentigo simplex is the most common form of lentigo. A single lesion or multiple lesions (lentigines) may be present at birth or more commonly first develop in early childhood. Lentigo simplex is not induced by sun exposure, and it is not associa ...
*
Solar lentigo Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicat ...
* Café au lait macule * 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 peel A chemical peel is a technique used to improve and smooth the texture of the skin. Facial skin is mostly treated, and scarring can be improved. Chemical peels are intended to remove the outermost layers of the skin. To accomplish this task, the ch ...
s *
Cryotherapy Cryotherapy, sometimes known as cold therapy, is the local or general use of low temperatures in medical therapy. Cryotherapy may be used to treat a variety of tissue lesions. The most prominent use of the term refers to the surgical treatment, s ...
*
Dermabrasion Dermabrasion is a type of surgical skin planing, generally with the goal of removing acne, scarring and other skin or tissue irregularities, typically performed in a professional medical setting by a dermatologist or plastic surgeon trained speci ...
* 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 *
Dysplastic nevus syndrome Dysplastic nevus syndrome, also known as familial atypical multiple mole–melanoma (FAMMM) syndrome, is an inherited cutaneous condition described in certain families, and characterized by unusual nevi and multiple inherited melanomas. First des ...
*
Epidermal nevus syndrome Epidermal nevus syndrome (also known as "Feuerstein and Mims syndrome", and "Solomon's syndrome"Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McGraw-Hill. .) is a rare disease that was first described in 19 ...
* Linear nevus sebaceous syndrome


Etymology

A naevus may also be spelled nevus. The plural is nevi or naevi. The word is from ''nævus'',
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
for " birthmark" and is correctly pronounced Nye-voos.


See also

*
Skin lesion A skin condition, also known as cutaneous condition, is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, nails, and related muscle and glands. The major function of th ...


References


External links

{{Authority control Dermatologic terminology Disturbances of human pigmentation Melanoma