Nevus () 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 injury or diseases. The term ''Lesion'' is derived from the Latin meaning "injury". Lesions may occur in both plants and animals. Types There is no de ...

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 ...

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 ...

. The term originates from , which is

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

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.

Classification

The term ''nevus'' is applied to a number of conditions caused by neoplasias 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 Tissue (biology), organic tissue that results from ...

s of

melanocyte Melanocytes are melanin-producing neural-crest, neural crest-derived cell (biology), cells located in the bottom layer (the stratum basale) of the skin's epidermis (skin), epidermis, the middle layer of the eye (the uvea), the inner ear, vagina ...

s, as well as a number of pigmentation disorders, both hypermelanotic (containing increased

melanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are ...

, 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 Human skin, skin. They are due to the development of abnormal cells (biology), cells that have the ability to invade or metastasis, spread to other parts of the body. It occurs when skin cells grow ...

Increased melanin

Usually acquired

Melanocytic nevus A melanocytic nevus (also known as nevocytic nevus, nevus-cell nevus, and commonly as a mole) is usually a Malignancy, noncancerous condition of pigment-producing Human skin, skin cells. It is a type of melanocytic tumor that contains nevus cell ...

** 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 Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

*** Intradermal:

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

*** 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 A blue nevus is a type of coloured mole, typically a single well-defined blue-black bump. The blue colour is caused by the pigment being deep in the skin. Diagnosis is by visualisation and dermoscopy. A biopsy is sometimes performed, or t ...

(rarely congenital): A classic blue nevus is usually smaller than 1 cm, flat, and blue-black in color. * Hori's nevus * Nevus spilus (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 is the most dangerous type of skin cancer; it develops from the melanin-producing cells known as melanocytes. It typically occurs in the skin, but may rarely occur in the mouth, intestines, or eye (uveal melanoma). In very rare case ...

, 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 A melanocytic nevus (also known as nevocytic nevus, nevus-cell nevus, and commonly as a mole) is usually a Malignancy, noncancerous condition of pigment-producing Human skin, skin cells. It is a type of melanocytic tumor that contains nevus cell ...

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 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 * 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, Dirk ( ...

* Eccrine nevus * Apocrine nevus

Connective tissue nevi

Connective tissue nevi represent abnormalities of

collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

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), 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 A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, an interventional radiologist, or an interventional cardiology, interventional cardiologist. The process involves the extraction of sampling (medicine), sample ...

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 is a form of immunostaining. It involves the process of selectively identifying antigens in cells and tissue, by exploiting the principle of Antibody, antibodies binding specifically to antigens in biological tissues. Alber ...

, 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 * 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 Cryotherapy, sometimes known as cold therapy, is the local or general use of low temperatures in medical therapy. Cryotherapy can be used in many ways, including whole body exposure for therapeutic health benefits or may be used locally to treat ...

* 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.

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 Epidermal nevus syndrome, also known as Feuerstein and Mims syndrome, and Solomon's syndromeFreedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McGraw-Hill. . is a rare disease that was first described in 1968 a ...

* Linear nevus sebaceous syndrome

References

External links

{{Authority control Dermatologic terminology Disturbances of human pigmentation