A congenitally determined tissue abnormality (or birthmark). In the skin, naeyi composed of tiny blood vessels are most common, but a mole is a melanocyte naevus, and warty, streaked and linear naevi of the epidermis occasionally occur.
Naevus is a form of skin imperfection. This condition is categorized into two primary groups: pigmented naevi, arising from irregularities or excessive activity of melanocytes (skin cells responsible for producing the brown pigment melanin); and vascular naevi, stemming from an unusual accumulation of blood vessels close to the skin’s surface.
The prevalent form of pigmented naevus is referred to as a freckle. Freckles manifest as small, flat, light-brown to dark-brown patches that can appear on any sun-exposed area of the body. The predisposition to develop freckles upon sun exposure is hereditary, and they are more commonly found in individuals with fair skin and red hair. Another variant is a lentigo, often known as an age spot or liver spot, which resembles a light-brown mark similar to a freckle. These spots tend to emerge in individuals over the age of 40, appearing on both covered and sun-exposed regions of the body. Café au lait spots constitute another type of light-brown pigmented naevus.
Another prevalent variant of pigmented naevus is a mole, also known as a melanocytic naevus. Moles exhibit a brown to dark-brown hue and typically have a diameter of less than 1 cm. They can emerge anywhere on the body, with a predisposition for their development sometimes being hereditary. Moles may become visible shortly after birth or during childhood and early adolescence. It’s common for adults to have around ten to 20 moles by the age of 30. The majority of moles are benign; however, in rare instances, a mole might undergo changes that render it cancerous. Red-brown naevi encountered during childhood are referred to as juvenile melanomas.
Certain naevi display a bluish hue. A considerable number of black and Asian newborns are born with blue-black markings on their lower backs.
Vascular naevi encompass port-wine stains and strawberry marks. Typically, these forms of naevi are apparent from birth. A port-wine stain presents as a red patch with an irregular shape, potentially causing distress, particularly when situated on the individual’s face. These marks usually persist permanently. Strawberry marks, frequently seen as birthmarks, manifest as elevated red swellings; they generally fade away by the time a child reaches about five years of age.
A spider naevus constitutes another instance of a vascular naevus. These occurrences are prevalent among children and expectant mothers.
The majority of naevi are benign. Nevertheless, if a naevus suddenly emerges, expands, starts to bleed, or undergoes a change in color, it is crucial to promptly seek medical guidance to rule out the possibility of skin cancer. For persistent birthmarks, laser treatment can be considered as a treatment option.