Factors that influence nevus pattern (age - skin type - body site)
Nevus pattern, Nevus classification, Dermoscopy, Benign nevi Factors that influence nevus pattern (age - skin type - body site) – cite! Factors that influence nevus pattern (age - skin type - body site) (message) Factors that influence nevus pattern (age - skin type - body site) – participate!
It is well known that the number of acquired melanocytic naevi varies with age; naevus counts increase steadily in youth and decrease after the fourth decade of life . Naevus counts in aged people decline due to the disappearance of reticular naevi. Contrarily, structureless and intradermal naevi seem to remain in the elderly  .
Recent dermoscopic studies suggest that the pattern of naevi also depends on age. Most studies investigating age related naevus patterns publish similar results, independent of the used classification for naevi. While clinical classiﬁcation comprises ﬂat, elevated and nodular types, dermoscopy identifies globular, reticular or mixed morphologies, with peripheral or central globules, or unspecified pattern .
In general, globular patterned naevi are the typical type among children and adolescents yet rarely seen in older age groups (present in <10% of all naevi in people over 60 years).  In particular, children often have naevi with a globular or structureless pattern (correlating with compound and dermal naevi, sometimes showing congenital-like features on histopathologic examination).
Reticular, homogeneous and reticular-homogeneous types of naevi are seen in individuals over 15 years old. In adults, most naevi show a reticular-homogeneous pattern (corresponding to lentiginous, junctional, or compound naevi)    .
A small subset of naevi in children and adolescents are composed of a central network or structureless area with peripheral small brown globules (as a sign of naevus growth). The number of this type of naevi increases from childhood, reaches peak prevalence in individuals between 11 and 20 years, and decreases rapidly thereafter. In a recent study, this pattern was no longer present in persons over 60 years old. Therefore, the management of lesions with peripheral globules becomes age dependent. In patients aged 50 or older, any melanocytic lesion showing peripheral globules should be considered highly unusual and excision is recommended. In patients aged 30 or older, naevi with peripheral globules should be checked up on regularly .
Counts of naevi with an unspecified pattern do not yet reach significance between the different age groups, thus they are not age dependent. However, naevi with an unspecified pattern are more common in in middle-aged persons compared to children and people over 50 years old .
In 16–30 year old individuals, naevi show a characteristic central hyperpigmentation. However, thus far no evident differences in pigmentation patterns are found in the older age groups .
These previous observations support the hypothesis that naevogenesis occurs by two distinct pathways   . The constitutional or endogenous pathway, which provides naevi with a globular, structureless, or unspecified dermoscopic pattern, occurs during childhood. These naevi represent persisting proliferations that later acquire the clinical appearance of an intradermal naevus   . The acquired or exogenous pathway is triggered by exposure to UV light, resulting in proliferating melanocytes in the epidermis, thereby producing naevi with a reticular pattern. Depending on age, reticular naevi appear and disappear, globular naevi arise at a young age and persist right through to old age .
An interesting observation is that naevi with peripheral globules are not only most prevalent in young adolescence but also prevalent during pregnancy. One explanation for the increased frequency of growing naevi could be the growth hormone rich environment in both periods. Another explanation for the higher prevalence of naevi with peripheral globules among youth is its temporary nature and, among elderly, these naevi transform into reticular or reticular-mixed patterns. The finding of a similar anatomic site related distribution for the different types of naevi is in line with this hypothesis .
A study by Zhang et al. assessed the number, distribution and dermoscopic pattern of naevi in a Chinese population, who had black eyes, dark hair and light skin with a yellowish tone. Age-related patterns of dermoscopy and naevi characteristics are proven to be similar to those recorded in previous studies of caucasian populations. In Chinese patients, total naevi counts on the body also increase with age from childhood to midlife and decrease again in older patients. As seen in previous findings in white people, this study identifies that patients’ predominant dermoscopic types of naevi differed across the age bands .
Fonseca et al reported a significant association of race, hair color and skin color with the relative frequency of reticular, globular, homogeneous and complex naevi on the back of adolescents (mean age 14 years). Hispanic ethnicity, darker hair color and darker skin color are associated with a relatively higher percentage of reticular back naevi and a lower percentage of homogeneous back naevi than non-Hispanic white ethnicity and lighter hair and skin colors, respectively. On the legs, skin color is also signiﬁcantly associated with naevus dermoscopic patterns, with subjects with darker skin having a higher percentage of reticular naevi and a lower percentage of homogeneous naevi than those with lighter skin .
Analysis of 300 naevi from subjects with skin type V and VI by Lallas et al. revealed signiﬁcant differences in the naevus pattern between these two groups. The majority of naevi in skin type V display a reticular pattern, whereas persons with skin type VI more frequently exhibit a structureless pattern. Black, blue and grey are more frequent in skin type VI, whereas the vast majority of naevi in Skin type V individuals show dark brown color .
Predominance of dermoscopic patterns of naevi is also body site dependent . Fonseca et al. reported the prevalence of dermoscopic patterns of acquired back and leg naevi in 8th and 9th grade adolescents (mean age 14 years): Globular naevi are signiﬁcantly more likely to be found on the back than on the legs, while reticular naevi are the most frequent dermoscopic naevus type on the legs .
In the following results from Zalaudek et al., the location on the trunk is subdivided into upper, middle, and lower segments on the anterior and posterior torso. Globular naevi are more prevalent on the upper segment compared with the middle segments of the trunk. Reticular naevi are common on the posterior middle segment of the torso. Naevi with a mixed pattern, composed of central globular / structureless area surrounded by a network, appear mostly on the anterior middle and posterior upper side of the trunk. Naevi with peripheral globules are generally infrequent and are most commonly located on the anterior and posterior middle segments of the trunk. Naevi with an unspecified pattern mostly reveal on the posterior upper and middle segment of the trunk .
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