Age-related prevalence of dermatoscopic patterns of acral melanocytic nevi

The objective of this study was to evaluate the relation between age and dermatoscopic features of acral nevi. We evaluated 159 dermatoscopic images of melanocytic nevi from 146 individuals filed at the Dermatoscopy Outpatient Clinic of Tokyo Women’s Medical University Medical Center East between April 2006 and March 2009. All images of melanocytic lesions on acral volar skin that showed a clear-cut dermatoscopic pattern of an acral nevus at the time of initial observation were included. The dermatoscopic patterns of all images were retrospectively examined in a blinded fashion according to the standard dermatoscopic classification criteria for acral melanocytic nevi. Images were classified using 15 structural variants of the parallel furrow pattern. These variants were then re-classified into two groups; the “single” line group and “double” line group. Patients of the double line group (age, 25.5 years) were significantly younger than those of the single line group (32.4 years). There was no significant difference in the age-related predominance between the solid line patterns and dotted line patterns. There was a significant age difference between patients with nevi showing the crista dotted pattern (mean age 24.9 years) and patients with nevi without the crista dotted pattern (mean age 34.6 years). We conclude that the double line variant of the parallel furrow pattern and crista dotted pattern, which probably correspond to the congenital type acral nevus, tend to be more common in young patients.

The objective of this study was to evaluate the relation between age and dermatoscopic features of acral nevi. We evaluated 159 dermatoscopic images of melanocytic nevi from 146 individuals filed at the Dermatoscopy Outpatient Clinic of Tokyo Women's Medical University Medical Center East between April 2006 and March 2009. All images of melanocytic lesions on acral volar skin that showed a clear-cut dermatoscopic pattern of an acral nevus at the time of initial observation were included. The dermatoscopic patterns of all images were retrospectively examined in a blinded fashion according to the standard dermatoscopic classification criteria for acral melanocytic nevi. Images were classified using 15 structural variants of the parallel furrow pattern. These variants were then re-classified into two groups; the "single" line group and "double" line group. Patients of the double line group (age, 25.5 years) were significantly younger than those of the single line group (32.4 years). There was no significant difference in the age-related predominance between the solid line patterns and dotted line patterns. There was a significant age difference between patients with nevi showing the crista dotted pattern (mean age 24.9 years) and patients with nevi without the crista dotted pattern (mean age 34.6 years). We conclude that the double line variant of the parallel furrow pattern and crista dotted pattern, which probably correspond to the congenital type acral nevus, tend to be more common in young patients.
ABSTRACT nevus within each of the age groups, absolute numbers and percentages are provided as frequencies.

Demographics of the study population and general results
We examined 159 melanocytic nevi in a study population of 146 individuals consisting of 47 men (32.2%) and 99 women (67.8%). The mean age of the study population was 29.8 years (range, 1-80 years). The distribution of nevi in the different age groups was 46 nevi in 0-15 years group, 29 nevi in the 16-30 years group, 55 nevi in the 31-45 years group, 20 nevi in the 46-60 years group and 9 nevi in the > 60 years age group. The mean age of each age group was 7.3, 26.8, 36.9, 50.9 and 70.0 years, respectively. The number of nevi on the palm was 9 (5.7%) while number of nevi on the plantar surface of the foot was 150 (94.3%).
In the parallel furrow group, the single solid line variant was identified in 74 lesions, of which 34 were prototypical single solid line variant only ( Figure 1A), 32 were associated with crista dotted pattern (regular dots/globules on the center of the ridges) ( Figure 1E), 1 was associated with crista reticulated pattern (reticular pigmentation on the ridges) ( Figure   1F) and 7 were associated with lattice-like pattern ( Figure   1G)

Age-related distribution of the structural dermatoscopic types of acral melanocytic nevi
The double line group pattern was the most predominant in the youngest age group (41.1%), but its frequency decreased with increasing age. On the other hand, the single line group was the most common (37.6%) in the third age group. The mean age of the double line group (25.5 years) was significantly lower than that of the single line group (32.4 years).

Age differences between subjects of the solid and dotted line patterns
We also analyzed differences in the age of patients with the solid and the dotted line patterns. The mean age was 31.5 TV and printed media, often emphasize this fact, recent recognition of acral melanoma has been increasing among the Japanese. One aspect of this awareness is wariness about the nature of any pigmented lesion that appears on the acral volar skin, with consequent increase in the number of consultations to dermatologists. On the other hand, acral melanocytic nevi are not rare and have an approximate incidence of 7 to 9% of the general Japanese population [3]. Therefore, it would be  Table 1. We then re-classified these 15 structural patterns into two groups, namely, the mean age for patients with nevi with crista dotted pattern was younger than those without the crista dotted pattern. These results showed significant age differences between nevi with crista dotted pattern and those without crista dotted pattern.

Discussion
The following are the major findings of our study.

Age differences between nevi with crista dotted pattern and nevi without crista dotted pattern
We also analyzed the age differences between patients with nevi with crista dotted pattern and those without crista dotted patterns. The mean age was 24.9 years for the nevi with crista dotted pattern, and 34.6 years for the nevi without crista dotted pattern. For both the single and double groups, the The limitations of the present study are the relatively small sample size, single medical center based study, single ethnicity, referral bias in the data set, cross-sectional and retrospective designs.
In conclusion, the double line variants of the parallel furrow pattern and crista dotted pattern, which probably correspond to the congenital type acral nevus, tend to be more common in young patients.