Nevus (or
naevus, plural
nevi, from
nævus, Latin for birthmark) is the medical term for sharply-circumscribed and
chronicChronic may refer to:* Chronic , a persistent and lasting disease or medical condition, or one that has developed slowly* Chronic toxicity,* The Chronic, a 1992 album by Dr. Dre...
lesionA lesion is any abnormal tissue found on or in an organism, usually damaged by disease or trauma. Lesion is derived from the Latin word laesio which means injury.-Causes of lesions:...
s of the
skinThe skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system made up of multiple layers of mesodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs. Skin of a different nature exists in amphibians, reptiles, birds...
. These lesions are commonly named
birthmarkA birthmark is a blemish on the skin formed before birth. A little over than 1 in 10 babies have a vascular birthmark. They are part of the group of skin lesions known as "naevi". The exact cause of most birthmarks is unknown, but vascular birthmarks are not hereditary.They are soft raised...
s and
molesA melanocytic nevus is a type of lesion that contains nevus cells.Some sources equate the term "mole" with "melanocytic nevus"...
. By definition, nevi are benign. Using the term nevus and nevi loosely, most physicians and dermatologists are actually referring to a variant of nevus called the "melanocytic nevus", which are composed of melanocytes.
Nevus (or
naevus, plural
nevi, from
nævus, Latin for birthmark) is the medical term for sharply-circumscribed and
chronicChronic may refer to:* Chronic , a persistent and lasting disease or medical condition, or one that has developed slowly* Chronic toxicity,* The Chronic, a 1992 album by Dr. Dre...
lesionA lesion is any abnormal tissue found on or in an organism, usually damaged by disease or trauma. Lesion is derived from the Latin word laesio which means injury.-Causes of lesions:...
s of the
skinThe skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system made up of multiple layers of mesodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs. Skin of a different nature exists in amphibians, reptiles, birds...
. These lesions are commonly named
birthmarkA birthmark is a blemish on the skin formed before birth. A little over than 1 in 10 babies have a vascular birthmark. They are part of the group of skin lesions known as "naevi". The exact cause of most birthmarks is unknown, but vascular birthmarks are not hereditary.They are soft raised...
s and
molesA melanocytic nevus is a type of lesion that contains nevus cells.Some sources equate the term "mole" with "melanocytic nevus"...
. By definition, nevi are benign. Using the term nevus and nevi loosely, most physicians and dermatologists are actually referring to a variant of nevus called the "melanocytic nevus", which are composed of melanocytes. Histologically, melanocytic nevi are differentiated from
lentiginesLentigo, plural "lentigines," a noun, is generally considered a brown pigmented spot on the skin. "Lentiginous", an adjective, is used to describe a skin lesion that fits the description of a "lentigo." Conditions characterized by lentigines include:...
(also a type of benign pigmented macule) by the presence of nests of melanocytes, which lentigines (plural form of lentigo) lack.
Classification
Classification is based on cell line of origin. Melanocytic nevi are derived from melanocytes. Epidermal nevi are derived from keratinocytes or derivatives of keratinocytes. Connective tissue nevi are derived from connective tissue cells like adipocyte and fibroblasts. Vascular nevi are derived from structures of the blood vessels.
See birthmarkA birthmark is a blemish on the skin formed before birth. A little over than 1 in 10 babies have a vascular birthmark. They are part of the group of skin lesions known as "naevi". The exact cause of most birthmarks is unknown, but vascular birthmarks are not hereditary.They are soft raised...
for a more complete discussion
Melanocytic nevus
- Congenital nevus implying a melanocytic nevus present at birth or near birth.
- Acquired melanocytic nevus
A melanocytic nevus is a type of lesion that contains nevus cells.Some sources equate the term "mole" with "melanocytic nevus"...
. Implies a melanocytic nevus acquired later in life, and not at or near birth. Most melanocytic nevi are of the acquired variety.
- Melanocytic nevus
A melanocytic nevus is a type of lesion that contains nevus cells.Some sources equate the term "mole" with "melanocytic nevus"...
(nevomelanocytic nevus, nevocellular nevus): benign proliferation of melanocyteMelanocytes are cells located in the bottom layer of the skin's epidermis, the middle layer of the eye , the inner ear, meninges, bones and heart that produce melanin which is a pigment.-Melanogenesis:...
s, the skin cells that make the brown pigment melaninMelanin is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. Many melanins are insoluble salts and show affinity to water...
. Hence, most nevi are brown to black. They are very common; almost all adults have at least one, usually more. They may be congenital or acquired (usually at puberty).
- Dysplastic nevus
A dysplastic nevus, is an atypical melanocytic nevus; a mole whose appearance is different from that of common moles. Dysplastic nevi are generally larger than ordinary moles and have irregular and indistinct borders...
usually an acquired melanocytic nevus with abnormal features making it difficult to distinguish from a melanomaMelanoma is a malignant tumor of melanocytes which are found predominantly in skin but also in the bowel and the eye . It is one of the less common types of skin cancer but causes the majority of skin cancer related deaths. Melanocytes are normally present in skin, being responsible for the...
. It can be a marker for an individual at risk for developing melanomas.
Epidermal nevus
- Epidermal nevus: congenital, flesh-colored, raised or warty, often linear lesion, usually on the upper half of the body.
- Nevus sebaceus: variant of epidermal nevus on the scalp presenting as a hairless, fleshy or yellowish area.
Vascular nevus
- Hemangioma
A hemangioma of infancy is a benign self-involuting tumour of endothelial cells . In most cases it appears during the first days or weeks of life and will have resolved at the latest by age 10...
(strawberry mark or nevus).
- Nevus flammeus (port-wine stain
A port-wine stain or naevus flammeus is a vascular birthmark consisting of superficial and deep dilated capillaries in the skin which produce a reddish to purplish discolouration of the skin. They are so called for their colour, resembling that of port wine. It is part of the family of disorders...
).
- Spider angioma
A spider angioma is a type of telangiectasis found slightly beneath the skin surface, often containing a central red spot and reddish extensions which radiate outwards like a spider's web...
(nevus araneus).
- Blue Rubber Bleb Nevus Syndrome
Blue rubber bleb nevus syndrome is a rare disorder that consists mainly of abnormal blood vessels affecting the gastrointestinal tract....
: dilatation of veins anywhere in the body (both skin and internal organs), usually lethal from internal hemorrhage. It is a very rare genetic disorder.
The term "venous nevus" has recently been proposed.
Diagnosis of nevi
Clinical diagnosis of a melanocytic nevus from other nevi can be made with the naked eye using the ABCD guideline, or using
dermatoscopyDermatoscopy is the examination of skin lesions with a dermatoscope, a magnifier with a light and a liquid medium between the instrument and the skin, thus illuminating the lesion without reflected light.This instrument is helpful to dermatologists in distinguishing benign from malignant...
. The main concern is distinguishing between a benign nevus, a
dysplastic nevusA dysplastic nevus, is an atypical melanocytic nevus; a mole whose appearance is different from that of common moles. Dysplastic nevi are generally larger than ordinary moles and have irregular and indistinct borders...
, and a
melanomaMelanoma is a malignant tumor of melanocytes which are found predominantly in skin but also in the bowel and the eye . It is one of the less common types of skin cancer but causes the majority of skin cancer related deaths. Melanocytes are normally present in skin, being responsible for the...
. Other skin tumors can resemble a melanocytic nevus clinically, such as a
seborrheic keratosisA seborrheic keratosis is a noncancerous benign skin growth that originates in keratinocytes. Like liver spots, seborrheic keratoses are seen more often as people age. In fact they are sometimes humorously referred to as the "barnacles of old age". They appear in various colors, from light tan to...
, pigmented basal cell cancer, hemangiomas, and
sebaceous hyperplasiaSebaceous hyperplasia is a disorder of the sebaceous glands in which they become enlarged. These glands are located within the skin and are responsible for secreting an oily substance named sebum. They are commonly associated with hair follicles but they can be found in hairless regions of the skin...
. A
skin biopsySkin biopsy is a biopsy technique in which a skin lesion is removed and sent to the pathologist to render a microscopic diagnosis. It is usually done under local anesthetic in a physician's office, and results are often available in 4 to 10 days. It is commonly performed by dermatologists. Skin...
is required when clinical dianosis is inadequate or when malignancy is suspected.
Normal Evolution or Maturation of Melanocytic Nevus
All melanocytic nevi will change with time - both congenital and acquired nevi. The "normal" maturation is evident as elevation of the lesion from a flat macule to a raised papule. The color change occur as the melanocytes clumps and migrates from the surface of the skin (epidermis) down deep into the dermis. The color will change from even brown, to speckled brown, and then losing the color and becomes flesh colored or pink. During the evolution, uneven migration can make the nevi look like melanomas, and
dermatoscopyDermatoscopy is the examination of skin lesions with a dermatoscope, a magnifier with a light and a liquid medium between the instrument and the skin, thus illuminating the lesion without reflected light.This instrument is helpful to dermatologists in distinguishing benign from malignant...
can help in differentiation between the benign and malignant lesions.
See also
- Becker's nevus
Becker's nevus is a skin disorder predominantly affecting males. The nevus generally first appears as an irregular pigmentation on the torso or upper arm , and gradually enlarges irregularly, becoming thickened and often hairy...
- Dysplastic nevus
A dysplastic nevus, is an atypical melanocytic nevus; a mole whose appearance is different from that of common moles. Dysplastic nevi are generally larger than ordinary moles and have irregular and indistinct borders...
- a melanocytic nevus with abnormal pigment features which can be difficult to distinguish from a melanoma.
External links