Also known as a mole, nevi is a benign growth that could appear like hyperpigmentation of the skin, colored macules, plaques or papules. Nevi are mostly congenital. They are confined to a particular area of the skin. They are also commonly referred to as birthmarks or beauty marks. Benign nevi typically means that the specific pigmented skin portion has not shown any signs of abnormality that is typical of skin cancer.
How do nevi occur?
Development of nevi is influenced by age of the person, environmental factors like sun exposure, race and genetic factors. It can develop in any part of the body though it can be predominant in sun-exposed areas like arms, face or neck when compared to intermittently exposed areas like chest, back or legs. Though most nevi are benign, 25% of malignant melanoma arise from pre-existing nevi.
For males, nevi are concentrated on the face and neck while for females nevi are concentrated on thighs and upper arms. Dark skinned individuals have a low count of total body nevus when compared to light skinned individuals. However dark skinned individuals develop nevi on the palms and soles. Nevi count in males is higher than in females. Nevi count in children depends on the nevi count in their parents. Commonly acquired nevi follow the ABCDE rule:
Nevi can be classified into different types as listed below
Connective tissue nevus: This type is very rare to occur; they are fleshy deep nodules.
Epidermal nevus: They are present at birth (congenital), and appear on the upper torso of the body. They resemble the color of flesh and appear raised or like a wart.
Nevus sebaceous: A variant of epidermal nevus, it appears on the scalp. The affected scalp area becomes hairless and looks yellowish in color. Melanocytic nevus: Benign production of melanocytes i.e. the skin cells make the brown pigment melanin. Therefore most of the nevi are brown to black in color. They are the common type of nevi and are present in almost all adults. They could be congenital or may develop at a later stage in life. Different types under melanocytic nevus are:
Acquired melanocytic nevus: Acquired at a later stage in life; will not be present in birth or near birth period.
Congenital nevus: Present from birth or near birth.
Dysplastic nevus: Acquired type of melanocytic nevus and difficult to differentiate from melanoma. It could be an indicator for the risk of developing melanoma.
Nevi are grouped based on their location. The different categories are:
Compound: They are hyper pigmented macules located in the epidermis and dermis.
Junctional: They are hyper pigmented macules located in the epidermis.
Intradermal: They are brown/skin colored papules located in the dermis layer.
Diagnosis and treatment of nevi
Diagnosis of nevi is generally done through visual examination; a dermatoscope may also be used. While diagnosing nevi, the main concern lies in identifying a benign nevus from a dysplastic nevus and melanoma. If physical examination doesn't suffice, a skin biopsy may help in identification.
Treatment for benign nevi
In general, benign nevi need not be treated. However a few may want it to be treated for cosmetic reasons. You can opt for laser treatment with a qualified skin specialist.
Protecting skin with nevi
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Bibliography / Reference
Collection of Pages - Last revised Date: October 30, 2020