Dermatoscopy of flat pigmented facial lesions—evolution of lentigo maligna diagnostic criteria

Recognition of facial lentigo maligna (LM) is often difficult, particularly at early stages. Algorithms and multivariate diagnostic models have recently been elaborated on the attempt to improve the diagnostic accuracy. We conducted a cross-sectional and retrospective study to evaluate dermatoscopic criteria aiding in diagnosis of flat pigmented facial lesions (FPFL). We examined 46 FPFL in 42 Caucasian patients and found that 4 of 20 dermatoscopic criteria reached the significance level required for features indicating malignancy namely, hyperpigmented follicular openings, obliterated follicular opening, annular-granular structures, and pigment rhomboids. Concomitant presence of at least 2 or 3 of the 4 mentioned criteria was significantly more frequent in LM than in pigmented actinic keratosis (PAK). However, despite more frequently seen in LM, these features were also displayed in some of the PAK and other FPFL, so we found them not specific for LM. Although dermatoscopy enhances the diagnostic accuracy in evaluating FPFL, histopathology remains the gold standard for correct diagnosis, making evident the need for improvements in early noninvasive diagnosis of LM.


Introduction
Flat pigmented facial lesions (FPFL) on chronic sun-damaged skin include a variety of melanocytic and nonmelanocytic, benign and malignant conditions with a similar clinical appearance presenting as a diagnostic challenge to physicians [1,2]. In many cases, diagnostic uncertainty is not resolved by clinical inspection, leading to biopsy or excision to rule out lentigo maligna (LM) [1].
Recognition of facial melanoma is often difficult, particularly in the early stages. Pigmented lesions of the face do not show the classic dermatoscopic findings characteristically observed elsewhere on the skin. A conventional pigment network is rarely found [2]. Instead, they are dermatoscopically characterized by the presence of a specific feature called a pseudonetwork [2][3][4]. The well-known "ABCDE rule" cannot be applied to facial locations [5,6]. Differential diagnosis includes solar lentigo (SL), postinflammatory hyperpigmen-Recognition of facial lentigo maligna (LM) is often difficult, particularly at early stages. Algorithms and multivariate diagnostic models have recently been elaborated on the attempt to improve the diagnostic accuracy. We conducted a cross-sectional and retrospective study to evaluate dermatoscopic criteria aiding in diagnosis of flat pigmented facial lesions (FPFL). We examined 46 FPFL in 42 Caucasian patients and found that 4 of 20 dermatoscopic criteria reached the significance level required for features indicating malignancy namely, hyperpigmented follicular openings, obliterated follicular opening, annular-granular structures, and pigment rhomboids. Concomitant presence of at least 2 or 3 of the 4 mentioned criteria was significantly more frequent in LM than in pigmented actinic keratosis (PAK). However, despite more frequently seen in LM, these features were also displayed in some of the PAK and other FPFL, so we found them not specific for LM. Although dermatoscopy enhances the diagnostic accuracy in evaluating FPFL, histopathology remains the gold standard for correct diagnosis, making evident the need for improvements in early noninvasive diagnosis of LM.

ABSTRACT
• Obliterated follicular opening (OFO), when obliterated hair follicles were seen; • Pigment rhomboids, interfollicular lines that form a polygon (most commonly a rhomboid); • Moth-eaten borders, defined as concave areas at the edge of the lesion; • Sharp border when there was abrupt cessation of pigmentation; • Scale , evaluated from the dermatoscopic not the clinical image after application of fluid or gel; • Fingerprint-like structures, corresponding to different types of fissures which can be described as ridges, "fat fingers," or cerebriform pattern; • Annular-granular structures, were considered when granules were found regularly around the follicles; • Red rhomboidal structure, defined as lozenge-shaped vascular pattern occurring in the area separating the hair follicles from each other; and • Increased density of the vascular network, defined as a vascular network of higher density within the lesion than in peripheral skin.

Data Analysis
All features were treated as binary values (present or absent).

Results
We examined 46 FPFL in 42 Caucasian patients (30 women and 12 men; age range 30-94 years, mean 65,2). LM was diag- Dermatoscopy has been demonstrated to be an efficient noninvasive technique for the preoperative assessment, as well as for differential diagnosis of pigmented lesions [5]. For all of these reasons, algorithms and multivariate diagnostic models have recently been elaborated on the attempt to improve the diagnostic accuracy [1,2,5,7].
The aim of the present study was to evaluate dermatoscopic criteria aiding in diagnosis of pigmented skin lesions on the face by blinded evaluation of a consecutive series of dermatoscopic images in order to emphasize their diagnostic value in the differentiation between LM and other FPFL.

Methods
We conducted a cross-sectional and retrospective study of the FPFL in patients attending one author's office over a 24-month period, from January 2014 to December 2015.
We excluded those lesions with equivocal histopathology reports, raised lesions, and lentigo maligna melanoma

Discussion
Caucasian skin chronically exposed to the sun is susceptible to both benign and malignant FPFL [1]. Lentigo maligna is the most common subtype of melanoma on the face with increasing incidence [5].
Despite a frequent delay in diagnosis, its prognosis at the time of diagnosis is globally good [5]. The high frequency of PAK observed in our study mainly reflects its relatively high frequency in the population when compared with LM [9]. Although dermatoscopic characteristics of LM on the face have been  Our analysis is in accordance with the first findings of Rosettes were solely observed in PAK. However, they can also be found in other non-melanocytic FPFL [1,9]. It must be emphasized that most dermatoscopic images were taken with non-polarized dermatoscope. Because rosettes are mainly visible with polarized light, we might have underestimated the presence of this structure. We found that pigment rhomboids and OFO were significantly more frequent in LM then in PAK but, again, were not specific.