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Table of Contents
Year : 2022  |  Volume : 40  |  Issue : 1  |  Page : 9-13

Site-specific dermoscopic features of lip lentigines, distinctive from those of facial lentigines

1 Department of General Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
2 Department of Public Health, Kaohsiung Medical University; Department of Environmental and Occupational Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
3 Department of Dermatology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
4 Department of Psychiatry, Kaohsiung Municipal Siaogang Hospital; Department of Psychiatry, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
5 Department of Dermatology, Kaohsiung Medical University Hospital; Department of Dermatology, Kaohsiung Medical University, Kaohsiung, Taiwan

Date of Submission01-Aug-2021
Date of Decision13-Oct-2021
Date of Acceptance18-Dec-2021
Date of Web Publication10-Mar-2022

Correspondence Address:
Dr. Shih-Tsung Cheng
No. 100, Tzyou 1st Rd., Sanmin Dist., Kaohsiung City 80756
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ds.ds_56_21

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Background: Lip lentigines are benign pigmentations often raising concerns to physicians and patients for fear of malignancy. Specific dermoscopic patterns of lip (mucosal) lentigines have not been clearly defined in the literature when compared to common facial (nonmucosal) lentigines. Objectives: This study aimed to define key dermoscopic features of lip lentigines to help diagnose these benign lesions more efficiently by calculating the specificity, sensitivity, and positive and negative predictive values (PPV and NPV) of dermoscopic patterns in lip and nonlip facial lentigines. Methods: A retrospective observational study was conducted at a medical center in Southern Taiwan. Dermoscopic images of 12 patients with lip lentigines and seven patients with 12 facial nonlip lentigines were inspected. Pattern recognition was performed via blind review by three clinicians. Dermoscopic images were assessed side by side with 12 published dermoscopic patterns of pigmented lesions, to see whether the patterns were presented. Results: Four dermoscopic patterns (hyphal, overlapping vessels, parallel lines, and fish-scale-like) showed very high specificity and PPV (all 100%) in lip lentigines when compared to facial nonlip lentigines. The sensitivity of these four patterns was 83%, 83%, 67%, and 58% and their NPV was 86%, 86%, 75%, and 71%, accordingly. Interrater consistency analysis from pattern recognition showed good consistency (Cronbach's alpha = 0.814) among reviewers. Conclusion: Hyphal, overlapping vessels, parallel lines, and fish-scale-like patterns are specific and sensitive dermoscopic patterns of lip lentigines when compared to facial nonlip lentigines. This knowledge of site-specific dermoscopic patterns could be used in characterizing benign and malignant pigmented lesions of the lip in future studies.

Keywords: Dermoscope, dermoscopic pattern, lentigo, lip, mucosa

How to cite this article:
Lin MC, Chuang HY, Lin SY, Ke CLK, Cheng ST. Site-specific dermoscopic features of lip lentigines, distinctive from those of facial lentigines. Dermatol Sin 2022;40:9-13

How to cite this URL:
Lin MC, Chuang HY, Lin SY, Ke CLK, Cheng ST. Site-specific dermoscopic features of lip lentigines, distinctive from those of facial lentigines. Dermatol Sin [serial online] 2022 [cited 2023 Mar 21];40:9-13. Available from: https://www.dermsinica.org/text.asp?2022/40/1/9/339332

  Introduction Top

Lip lentigines, or labial melanotic macules, are asymptomatic benign pigmentations found on the lip. Lesions are mostly found on the lower lip, indicating its relation to sun exposure, similar to facial lentigines which are commonly seen on the sun-exposed skin on the face. Though benign, its macroscopic appearance might resemble malignant pigmented lesions in the lip,[1] which are more prevalent in Asians,[2],[3] and poses concerns to both patients and dermatologists. Biopsy of lip lentigines is a gold standard to rule out malignancy but may be complicated with local swelling, pain, speaking difficulties, poor healing of wound, infection, sometimes leaving unsightly scars.[4] Recently, dermoscopy revealed details of skin lesions not visible to the naked eye, which has been helpful in diagnosing pigmented skin lesions, thus reducing the necessity of invasive surgical procedures.[5]

Dermoscopy is also useful in determining the diagnosis of pigmented lesions on different anatomic sites. Saida et al. found that pigmented lesions on the volar skin exhibit parallel pattern which is different from that of pigmented lesions on the nonglabrous skin, reflecting underlying arrangement and configuration of epidermal rete ridges in glabrous and nonglabrous skin.[2],[3],[6] This unique dermoscopic pattern was then applied to define different characteristics between benign and malignant pigmented lesions on the glabrous skin.[6],[7],[8],[9] In analogy to the glabrous versus nonglabrous pigmented lesions, the comparison between lip (mucosal) and facial nonlip (nonmucosal) lentigines may give us insight to the unique site-specific features of pigmented lesions on the lip, which may be useful in defining different characteristics between benign and malignant pigmented lesions of the lip.

No established clinical definite diagnosis criteria were proposed for differentiating common lentigines, congenital melanocytic nevus, or malignancies; however, these pigmented lesions often present with distinctive dermoscopic features.[10],[11],[12] Characteristic lip lentigines often feature as brownish, flat, small, located on the lower lip with slow growth rate, while oral melanomas often occur predominantly in senile patients, often melanotic, ulcerative, or bleeding. Characteristic lip lentigo dermoscopic pattern features lines, circles, clods, or dots, while mucosal melanoma dermoscopic patterns feature color variegation and atypical network.[13],[14],[15],[16]

A variety of dermoscopic patterns of lip lentigines have been previously published by several authors.[13],[15],[16],[17] Lin et al. reported that “fish-scale-like,” “hyphal,” “dotted-globular,” and “homogenous” patterns are closely associated with mucosal melanotic macules.[16] Kim et al. concluded that benign labial melanotic macules are characterized by “background brown pigmentations,” “circles,” “overlapping vessels,” and “parallel lines” (so-called “landscape painting patterns”).[15] Dermoscopic patterns of “dotted-globular,” “homogenous,” “parallel lines,” “structureless,” “circles,” “reticular,” “globules or clods,” and “dots” have been well characterized in describing nonlip lentigines.[17],[18],[19] Four out of the 12 patterns listed above have been reported in both lip and nonlip lentigines [see the intersection of [Figure 1]].[17],[18],[19]
Figure 1: Dermoscopic patterns of lip (left circle), nonlip lentigines (right circle), and their intersection (patterns of both lip and nonlip lentigines), published in previous literature.

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To better understand the distinctive features of lip and facial nonlip lentigines, we calculated the statistical values of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of dermoscopic patterns of these two pigmented lesions.

  Methods Top

Twelve Taiwanese patients with lip lentigines (four males and eight females aged from 21 to 74 years) and seven patients with 12 facial nonlip lentigines (five males and two females aged from 23 to 25 years) were collected from 2008 to 2019 at the dermatology outpatient department of a medical center. The study was approved by the ethics committee at where the research was conducted (approval number: KMUHIRB-E(II)-20190127). The patient consent was waived by the IRB. All of the patients have been diagnosed by clinical and dermoscopic examinations [Figure 2]. Nine out of 12 patients with lip lentigines received histological confirmation. Dermoscopic photography was recorded by a polarized dermoscope (3Gen DermLite FOTO) connected to a digital camera (Canon PowerShot G15).
Figure 2: Flow diagram of methods in this study. The dermoscopic images of patients with lip and facial nonlip lentigines were collected retrospectively, set side by side for comparison with previously published dermoscopic patterns of lip and nonlip pigmented lesions, and then sent for blind review by three clinicians (site of lentigines were withheld). The interrater consistency of reading results were calculated by Cronbach's alpha using SPSS 20. The sensitivity, specificity, PPV and NPV of each dermoscopic pattern in lip and nonlip lentigines were calculated, respectively. PPV: Positive predictive value, NPV: Negative predictive value.

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Image pattern recognition was performed. Twelve published dermoscopic patterns in previous studies of pigmented lesions [listed in Figure 1] were blindly assessed side by side with 24 dermoscopic images (12 lip and 12 facial lentigines) by three experienced clinicians independently, to see if the pattern was present in the dermoscopic image. If the opinions were not consistent among the three, the result was determined by two-to-one majority. The interrater consistency among the three reviewers was then calculated by Cronbach's alpha in SPSS 20 statistical package (SPSS, Inc., Chicago, IL, USA). Total consistency was determined by number of unanimous reading results divided by number of total questions. The respective sensitivity, specificity, PPV, and NPV of each dermoscopic pattern were calculated accordingly.

  Results Top

Patient demographics

The age of the 12 recruited patients (33.3% male) with lip lentigines ranged from 21 to 74 years (mean age 39.4, standard deviation 16.2). The skin types of the patients were either Fitzpatrick skin type IV to type V. The age of the 7 recruited patients (71.4% of male) with facial nonlip lentigines ranged from 23 to 25 years (mean age 23.7, standard deviation 0.95); the skin types of the patients were Fitzpatrick type IV.

Site and size of lentigines

The average size of the lip lentigines was 0.6 cm (0.1–3 cm). Eleven of the twelve patients with lip lentigines had single presentations and one presented with multiple patches. Of the patient with multiple lesions, no history of  Peutz-Jeghers syndrome More Details or other related diseases was noted. The average size of the facial lentigines was 0.2 cm (0.1–0.3 cm). The lentigines were located on forehead, temple, and cheek.

Statistical reliability analysis

The results of dermoscopic pattern assessment from the three reviewers showed good interrater consistency by reliability analysis using Cronbach's alpha (alpha = 0.814), indicating conformity among the reviewers. Consistency of the three reviewer readings was 0.70 totally.

Sensitivity and specificity

Four patterns, hyphal, overlapping vessels, fish-scale-like pattern, and parallel lines [Figure 3], showed high specificities and PPV (all 100%) in lip lentigines [Table 1]. Their sensitivities were 83%, 83%, 58%, and 67%; their NPVs were 86%, 86%, 71%, and 75%, respectively [Table 1]. The first three patterns were found solely in the literature of lip lentigines, while parallel lines were described in both lip and facial literature [Figure 1]. Background brown pigmentations scored 100% sensitivity but low specificity (0%) and relatively low PPV (50%).
Figure 3: Four clinical images of dermoscopic patterns with high specificity, sensitivity, PPV, and NPV in lip lentigines. (a) Hyphal pattern, (b) overlapping vessels, (c) parallel lines, (d) fish-scale-like pattern. PPV: Positive predictive value, NPV: Negative predictive value.

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Table 1: Statistical values of dermoscopic patterns

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Four patterns (circles, structureless patterns, reticular pattern, and globules or clods) showed relatively high specificity (100%, 75%, 92%, and 83%, respectively) and PPV (100%, 75%, 75%, and 75%) in facial lentigines [Table 1]. The latter two patterns were found solely in the literature of nonlip lentigines, while the former two patterns were described in both lip and nonlip literature [Figure 1]. Of the four patterns, only structureless pattern showed higher sensitivity (75%) and NPV (75%) in facial lentigines [Table 1]. On the contrary, homogenous patterns showed high sensitivity (100%) and NPV (100%) but low specificity (50%) and PPV (67%) in facial lentigines [Table 1].

Interestingly, we found that lip lentigines involving the vermillion part of the lip often present with fish-scale-like pattern (7/11, 63.6%), while lip lentigines commonly present with overlapping vessels (5/9, 55.6%) (data not shown).

To summarize, “hyphal pattern,” “overlapping vessels,” “fish-scale-like pattern,” and “parallel lines” are the four highly specific and remarkably sensitive features of lip lentigines compared to facial nonlip lentigines in this study.

  Discussion Top

Previous studies have reported dermoscopic patterns of lip lentigines; however, the specificities of these patterns in lip lentigines, when compared with other common facial nonlip lentigines, are not known. Since both lip and facial nonlip lentigines are sun related, dermoscopic patterns shared by these two pigmented lesions might be included in previous studies. In this study, we calculated the sensitivity, specificity, PPV, and NPV of these patterns, identified highly specific and remarkably sensitive patterns of lip lentigines, and factored out nonspecific patterns of the lip which were also found in facial nonlip lentigines. This knowledge of site-specific patterns is useful in characterizing pigmented lesions of the lip in contrast to the common facial lentigines. We also found that the inter-reviewer agreement (interrater reliability) on the reading results of pattern recognition among three reviewers is consistent, therefore validating the specificities of the dermoscopic patterns on lip lentigines.

The underlying structures of “hyphal,” “parallel lines,” and “fish-scale-like” pattern in the lip lentigines are not known. We speculate that it may be caused by melanin of melanocytes residing in epidermal rete ridges underlying the lip. “Overlapping vessels” pattern in lip lentigines is likely to be contributed by thin stratum corneum and abundant vasculature uniquely found in the lip mucosa.

”Background brown pigmentations,” originally described solely in lip lentigines [left circle, [Figure 1]], was found to have high sensitivity but low specificity in lip lentigines. Patterns, “dotted-globular” and “homogenous” patterns,[13],[15],[16] possessing high sensitivities but low specificities in both lip and nonlip lentigines in our study, are therefore common patterns found in both lip and facial lentigines, suggesting a common causative agent, such as sun exposure. “Circles,” “structureless,” “reticular,” “globules or clods” patterns showed that high specificity and PPV in facial nonlip lentigines can be categorized as key dermoscopic features of facial lentigines.


This study was an open-label, case–controlled, retrospective review of patients with lip lentigines compared with facial nonlip lentigines. The number of cases was limited which may not reflect the general population. Three patients with lip lentigines who did not receive lip biopsy remained disease-free after 3 years of follow-up. The facial lentigines were presented on the recruited patients for many years, and also, no sign of malignant change or increase of size was noted over the years. We believe that considering the complications of skin biopsy, not all biopsies were necessary in the clinical scenario. We did not investigate dermoscopic patterns of malignant pigmented lesions, such as melanomas and basal cell carcinomas, on the lip. Further study is needed.

  Conclusion Top

Our study found that lip lentigines exhibit highly site-specific and remarkably sensitive dermoscopic patterns, including “hyphal,” “overlapping vessels,” “parallel lines,” and “fish-scale-like” patterns, distinctive from common facial lentigines.


The authors thank dermatologist Stephen Chu-Sung Hu from Kaohsiung Medical University Hospital for his professional opinion on dermoscopy and professional assistance.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1]


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