This article presents an overview of the history and development of dermatoscopy over the last 2 decades. The common dermatoscopic diagnostic algorithms are discussed, including classic pattern analysis, the ABCD rule (asymmetry, border, color, and dermatoscopic structures), 7-point checklist, and Menzies method, as well as a new method by the authors (ASAP: a simple and practical approach). In addition, evidence on the clinical impact and challenges of dermatoscopy for the diagnosis and management of pigmented lesions and the importance of training are reviewed.
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Dermatoscopy is a noninvasive tool that can improve the accuracy of diagnosing melanoma and pigmented lesions.
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The use of routine dermatoscopy can reduce the rate of excision of benign lesions.
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There are several diagnostic algorithms that are used by dermatologists.
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The optimal diagnostic approach to melanoma and pigmented lesions is a combination of clinical exam and different imaging techniques.
Introduction
Dermatoscopy, also known as dermoscopy, epiluminescence microscopy, incident light microscopy, and skin surface microscopy, is a noninvasive diagnostic technique that uses a magnifying device to observe skin lesions in vivo. Dermatoscopy allows for visualization of subsurface structures that are not otherwise visible to the naked eye, and also has established correlations to histopathologic structures ( Fig. 1 ).
The use of dermatoscopy in the evaluation and diagnosis of pigmented lesions has increased over the last several decades, particularly for the early detection of melanoma. Despite the increased survival rates over the last 30 years, melanoma is one of the top 10 primary cancer sites, with the highest rates of incidence in the United States. Among the public education initiatives and the advent of new technologies, dermatoscopy has emerged as an important noninvasive technique that improves the ability to detect melanoma at early stages associated with high rates of cure.
This article reviews the history of dermatoscopy and the evolution of its use by dermatologists, the range of algorithms used to interpret dermatoscopic images, and the clinical efficacy and challenges of dermatoscopy in the management of melanoma and pigmented lesions.
History of dermatoscopy and its uses
Dermatoscopy is the use of a microscope that allows dermatologists to visualize subsurface structures from the epidermis to the superficial papillary dermis that are not otherwise visible to the naked eye. Traditional dermatoscopes use nonpolarized light sources against an oil or alcohol interface to decrease light reflection, refraction, and diffraction, making the epidermis more translucent. Newer polarized light dermatoscopes have been developed that do not require a fluid interface.
The use of dermatoscopy has dated as far back as the seventeenth century, but it was not until the 1980s that studies showed the usefulness of dermatoscopy in the diagnosis of pigmented skin lesions through the analysis of patterns. In 1987, Pehamberger and colleagues published the common dermatoscopic features of melanocytic and nonmelanocytic lesions, which has laid the foundation of diagnostic dermatoscopic methods. In 1989, Soyer and colleagues correlated dermatoscopic structures to histopathologic structures, establishing dermatoscopy as a link between clinical and histopathologic views. In the same year, dermatoscopic terminology was defined at the First Consensus Conference on Skin Surface Microscopy in Hamburg, Germany to standardize the use of this technology.
Worldwide interest in the use of dermatoscopy for the diagnosis of melanoma and pigmented lesions has increased over the past 2 decades. Between 1985 and 2009, the scientific output in dermatoscopy increased significantly, resulting in publications in high-impact dermatology journals including Archives of Dermatology , Journal of the American Academy of Dermatology , and British Journal of Dermatology . The largest proportion of dermatoscopy publications were from Italy (29%), followed by the United States (22%) and Austria (15%).
In addition to increases in scientific output, the development of easier-to-use, handheld dermatoscopes, along with increased dermatoscopy training have led to the increased prevalence of its use by clinicians. The newer, polarized noncontact dermatoscopes that do not require fluid interface are convenient for clinicians because of the small size and portable nature of these devices. Although there are some differences among the dermatoscopes in the representation of certain colors such as the blue-white veil and pink or red, the capabilities of each device are complementary.
Worldwide, the prevalence of the use of dermatoscopy has been studied through survey methods. In a survey of the practices of dermatoscopy among US dermatologists in 2001, 17% of responding dermatologists from the American Board of Medical Specialists Directory of Board Certified Medical Specialists reported using dermatoscopy to aid in clinical assessment, compared with 57% using a magnifying lens. Since then, dermatoscopy practices have increased significantly, ranging from 51% of respondents in a survey of academic dermatology training programs to 70% of survey respondents attending a dermatoscopy seminar at the American Academy of Dermatology’s Summer Academy meeting in 2007. The most common reported reasons for using dermatoscopy across survey studies was the belief that it aided in the early detection of melanoma, led to fewer biopsies, and reduced patient anxiety. Current dermatoscopy users also rated the importance of dermatoscopy in the daily evaluation of skin lesions a mean of 7.4 on a scale of 1 to 10, with 1 representing no importance and 10 representing utmost importance. For dermatologists not using dermatoscopy, lack of training and the lack of usefulness were the most common reasons.
In Australia, a survey assessing the prevalence and attitude toward dermatoscopy revealed that 98% of respondent dermatologists used dermatoscopy, of whom 95% received formal dermatoscopy training. Dermatologists who used dermatoscopy felt more confident with their clinical diagnosis with the addition of dermatoscopy (92%) and believed their diagnosis was more accurate than with the naked eye examination alone (86%). Furthermore, respondents believed that dermatoscopy enabled them to detect melanoma at earlier, curable stages (78%), and led to fewer biopsies (72%). A small percentage (3%) believed that dermatoscopy was not useful for the diagnosis of pigmented lesions, melanoma, or atypical nevi, and 12% believed that it was not useful for the diagnosis of nonpigmented lesions.
In Europe, the use of dermatoscopy was documented in the Euromelanoma skin cancer prevention campaign. This campaign was a joint initiative of 20 European countries that was developed to screen for skin cancer. Among nearly 60,000 subjects screened, dermatoscopy was used to aid in 78% of clinical examinations for suspected melanoma.
Since the first efforts to characterize dermatoscopic patterns in the 1980s, the use of dermatoscopy for melanoma and pigmented lesions has increased in prevalence worldwide. The major barrier to its use is the lack of training and understanding of the dermatoscopic diagnostic patterns and algorithms.
History of dermatoscopy and its uses
Dermatoscopy is the use of a microscope that allows dermatologists to visualize subsurface structures from the epidermis to the superficial papillary dermis that are not otherwise visible to the naked eye. Traditional dermatoscopes use nonpolarized light sources against an oil or alcohol interface to decrease light reflection, refraction, and diffraction, making the epidermis more translucent. Newer polarized light dermatoscopes have been developed that do not require a fluid interface.
The use of dermatoscopy has dated as far back as the seventeenth century, but it was not until the 1980s that studies showed the usefulness of dermatoscopy in the diagnosis of pigmented skin lesions through the analysis of patterns. In 1987, Pehamberger and colleagues published the common dermatoscopic features of melanocytic and nonmelanocytic lesions, which has laid the foundation of diagnostic dermatoscopic methods. In 1989, Soyer and colleagues correlated dermatoscopic structures to histopathologic structures, establishing dermatoscopy as a link between clinical and histopathologic views. In the same year, dermatoscopic terminology was defined at the First Consensus Conference on Skin Surface Microscopy in Hamburg, Germany to standardize the use of this technology.
Worldwide interest in the use of dermatoscopy for the diagnosis of melanoma and pigmented lesions has increased over the past 2 decades. Between 1985 and 2009, the scientific output in dermatoscopy increased significantly, resulting in publications in high-impact dermatology journals including Archives of Dermatology , Journal of the American Academy of Dermatology , and British Journal of Dermatology . The largest proportion of dermatoscopy publications were from Italy (29%), followed by the United States (22%) and Austria (15%).
In addition to increases in scientific output, the development of easier-to-use, handheld dermatoscopes, along with increased dermatoscopy training have led to the increased prevalence of its use by clinicians. The newer, polarized noncontact dermatoscopes that do not require fluid interface are convenient for clinicians because of the small size and portable nature of these devices. Although there are some differences among the dermatoscopes in the representation of certain colors such as the blue-white veil and pink or red, the capabilities of each device are complementary.
Worldwide, the prevalence of the use of dermatoscopy has been studied through survey methods. In a survey of the practices of dermatoscopy among US dermatologists in 2001, 17% of responding dermatologists from the American Board of Medical Specialists Directory of Board Certified Medical Specialists reported using dermatoscopy to aid in clinical assessment, compared with 57% using a magnifying lens. Since then, dermatoscopy practices have increased significantly, ranging from 51% of respondents in a survey of academic dermatology training programs to 70% of survey respondents attending a dermatoscopy seminar at the American Academy of Dermatology’s Summer Academy meeting in 2007. The most common reported reasons for using dermatoscopy across survey studies was the belief that it aided in the early detection of melanoma, led to fewer biopsies, and reduced patient anxiety. Current dermatoscopy users also rated the importance of dermatoscopy in the daily evaluation of skin lesions a mean of 7.4 on a scale of 1 to 10, with 1 representing no importance and 10 representing utmost importance. For dermatologists not using dermatoscopy, lack of training and the lack of usefulness were the most common reasons.
In Australia, a survey assessing the prevalence and attitude toward dermatoscopy revealed that 98% of respondent dermatologists used dermatoscopy, of whom 95% received formal dermatoscopy training. Dermatologists who used dermatoscopy felt more confident with their clinical diagnosis with the addition of dermatoscopy (92%) and believed their diagnosis was more accurate than with the naked eye examination alone (86%). Furthermore, respondents believed that dermatoscopy enabled them to detect melanoma at earlier, curable stages (78%), and led to fewer biopsies (72%). A small percentage (3%) believed that dermatoscopy was not useful for the diagnosis of pigmented lesions, melanoma, or atypical nevi, and 12% believed that it was not useful for the diagnosis of nonpigmented lesions.
In Europe, the use of dermatoscopy was documented in the Euromelanoma skin cancer prevention campaign. This campaign was a joint initiative of 20 European countries that was developed to screen for skin cancer. Among nearly 60,000 subjects screened, dermatoscopy was used to aid in 78% of clinical examinations for suspected melanoma.
Since the first efforts to characterize dermatoscopic patterns in the 1980s, the use of dermatoscopy for melanoma and pigmented lesions has increased in prevalence worldwide. The major barrier to its use is the lack of training and understanding of the dermatoscopic diagnostic patterns and algorithms.
Dermatoscopic diagnostic algorithms
Various models are used to interpret dermatoscopic images of pigmented skin lesions. The primary goal of most of these algorithms is to distinguish between benign and malignant melanocytic lesions. The most widely used dermatoscopic algorithms are pattern analysis, the ABCD rule (asymmetry, border, color, and dermatoscopic structures), the Menzies method, and the 7-point checklist. The virtual Consensus Net Meeting on Dermoscopy, an Internet meeting of 40 experienced dermatologists, evaluated the reproducibility and validity of these 4 algorithms by assessing diagnostic performance and interobserver and intraobserver agreement of 108 dermatoscopic images. The results of the consensus meeting showed that all 4 algorithms were valid ways to evaluate melanocytic lesions with dermatoscopy when used by experienced dermatologists.
More recently, Henning and colleagues described the CASH algorithm (color, architecture, symmetry, and homogeneity) for dermatoscopy, and Rao and colleagues described a simple and practical approach (ASAP) to dermatoscopy. This section reviews each dermatoscopic algorithm and the comparisons of diagnostic accuracy in the literature.
Pattern Analysis
Pattern analysis of pigmented lesions is a qualitative analysis that assesses the diagnostic value of all of the lesion parameters detectable on dermatoscopy. In 1987, Pehamberger and colleagues analyzed more than 3000 pigmented lesions using dermatoscopy to define morphologic criteria that represented reliable markers of benign and malignant skin lesions. Each lesion was excised after dermatoscopic examination to verify the diagnosis through histopathologic examination of serial sections and to correlate dermatoscopic features to histopathologic features. This study established the dermatoscopic patterns for both melanocytic and nonmelanocytic pigmented lesions, and particularly for benign versus malignant growth patterns. The criteria in this study remain influential, serving as the basis for newer algorithms that simplify the dermatoscopic approach to pigmented lesions. Pattern analysis in some variation is still the most commonly used diagnostic method to evaluate dermatoscopic images, reportedly used in as many of 90% of respondents in a survey of dermatologists who use dermatoscopy.
The criteria that were used to distinguish between benign and malignant growth patterns in pigmented skin lesions were based on the general appearance, the pattern of pigmentation, color, pigment network, the presence of globules and dots, depigmentation, and the margin of the pigmented skin lesion. These criteria are defined as follows:
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General appearance: assessment of the general appearance of a lesion is based on the uniformity or heterogeneity of the lesion, the profile of the lesion (elevated or depressed relative to the surrounding skin), and the surface texture of the lesion.
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Pattern of pigmentation: this refers to the color and intensity of pigmentation, and specific pigmentation patterns such as a pigment network, dots, and globule.
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Color: colors seen on dermatoscopy are based on the location of melanin in the skin; from superficial to deep, black indicates melanin in the epidermis, light brown to dark brown indicates melanin at the dermoepidermal junction, gray indicates melanin at the papillary dermis, and steel blue indicates melanin in the reticular dermis.
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Pigment network: the pigment network is a subtle network of brown lines over the background tan color of skin, which result from the presence of melanin pigment in the epidermal basal cell layers that project to the skin surface in rete ridges. The appearance of the pigment network depends on the organization of the rete ridges. An irregular pigment network indicates disorderly spaced rete ridges.
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Brown globules: nests of melanin-containing melanocytes in the lower epidermis appear as brown globules. In benign lesions, they are uniform in size and distribution. In dysplastic or malignant pigmented lesions, brown globules vary in size and appear irregular in distribution.
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Black dots: melanin concentrated in cornified layers of the epidermis appears as black dots. In benign lesions, black dots are typically seen in the center of the lesion. In dysplastic or malignant lesions, black dots may spread out to the periphery.
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Depigmentation: absence of pigment and regression of pigment appear as areas of depigmentation relative to surrounding skin. In benign lesions, depigmentation may occur but appears regular and contained within the center of the lesion. In dysplastic or malignant lesions, depigmentation is irregular and may be found anywhere in the lesion.
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Margin of pigmented skin lesions: the margin of pigmentation can be regular or irregular, and can be well defined or thin out into the surrounding skin. Benign skin lesions have margins of gradually thinning out pigmentation. Malignant pigmented skin lesions have irregular borders and often show areas of abrupt pigmentation margins.
Pattern analysis of dermatoscopic morphologic features can distinguish between pigmented lesions that appear similar clinically but may range from benign to melanoma ( Table 1 ). Pattern analysis is also useful in identifying benign nonmelanocytic pigmented lesions such as seborrheic keratosis, hemangioma, and malignant nonmelanocytic pigmented lesions such as pigmented basal cell carcinoma ( Figs. 2–4 ).
| Lesion Type | General Appearance | Surface | Pigment Pattern | Border | Depigmentation (Hypopigmentation) |
|---|---|---|---|---|---|
| Junctional nevus | Orderly; uniform | Skin surface preserved or smooth; no scales | Regular pigment network at periphery (usually blurred); brown globules equal size and regularly spaced along meshes of pigment network; Intense uniform pigmentation in center pigment network; black dots may occur in center of lesion | Regular; simple outline, pigment network thins out at periphery; no pseudopods; no radial streaming | Usually absent |
| Compound nevus | Orderly | Skin surface coarse; hyperkeratotic, smooth | Regular; well defined | ||
| Lentigo maligna melanoma in situ | Polymorphous; multiple patterns | Skin surface preserved; flat | Prominent but highly irregular pigment network, often obscured by uniform pigmentation; black dots at periphery | Pigment network stops abruptly at edge; no pseudopods, radial streaming may be present | White and pink regions of depigmentation with irregular outline |
| Lentigo maligna melanoma invasive | Polymorphous; multiple patterns | Skin surface preserved in flat areas; loss of normal skin surface in nodular areas | Highly irregular, prominent pigment network, black dots at periphery; loss of pigment network in nodular areas | Pigment network stops abruptly at edge; pseudopods and radial streaming | White and pink regions of depigmentation with irregular outline |
| Dysplastic nevus (I and II) | Polymorphous | I: Flat II: Macular with papular component; skin surface not preserved; irregular | I: Prominent pigment network, focally irregular; brown globules of variable size haphazardly spaced; patches of uniform hyperpigmentation; black dots II: No pigment network; irregular brown globules aggregated in center or periphery; irregular depigmentation; black dots, target lesionlike appearance | Irregular, semicircular extensions at periphery; focally pigment network stops abruptly at periphery; peripheral aggregation of brown globules; no radial streaming | I: Not frequent II: Irregular, center, and periphery |
| Superficial spreading melanoma | Polymorphous; multiple patterns | Skin surface not preserved; slightly elevated, irregular | Irregular, prominent pigment network; brown to black globules of variable size haphazardly spaced; intensely colored patches; black dots at periphery; areas of uniform pigmentation varying in size and ranging in color (blue-gray to black) | Pigment network irregular, stops abruptly at the edge; pseudopods and radial streaming | Bizarre; pink or white |
| Nodular melanoma | Polymorphous or uniform | Skin surface not preserved; nodular, smooth, or hyperkeratotic | Usually uniformly pigmented; thin rim of prominent and irregular pigment network at periphery; black dots at peripheral areas of uniform pigmentation from gray, blue, brown, to black | Pigment network irregular, stops abruptly at the edge, pseudopods either black or blue; radial streaming | White and pink regions with irregular outline; often speckled with black and blue dots |
| Angioma | Monomorphous; orderly | Skin surface not preserved; papular | No pigment pattern | Regular; well defined | Absent |
| Pigmented basal cell carcinoma | Polymorphous | Skin surface not preserved; macular or papular; irregular | No pigment pattern except black dots; telangiectasia | Irregular; no pigment network; no pseudopods; no radial streaming; telangiectasia | Irregular |
| Seborrheic keratosis | Polymorphous | Skin surface not preserved; verrucous, horny plugs | No pigment pattern except black dots and streaks of pigment; brownish appearance | Irregular | Absent |
ABCD Rule
The ABCD rule of dermatoscopy was the second algorithm for dermatoscopy that was developed as a simplification of pattern analysis. The 4 criteria that comprise the algorithm are asymmetry, border, color, and dermatoscopic structural components. Among the 31 dermatoscopic criteria described in the pattern analysis method, these criteria were the most significant cofactors for diagnosing melanoma. In this semiquantitative model, each of the 4 criteria is scored out of a variable number of maximum points and then applied to a formula that adjusts the points with conversion factors, yielding a total dermatoscopic score (TDS). According to this algorithm, lesions with TDS less than 4.75 are usually benign, a TDS between 4.80 and 5.45 is suggestive but not diagnostic of melanoma, and a TDS greater than 5.45 is highly suspicious of melanoma. Lesions with equivocal TDS (4.80–5.45) may be excised or followed to look for dermatoscopic changes over time ( Table 2 ). Each component of the ABCD rule is described as follows:
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Asymmetry: the asymmetry score is determined by visually dividing the lesion into 2 90 ° axes to assess mirror symmetry in terms of contour, color, or structure ( Fig. 5 A). Asymmetry is scored from 0 to 2. A lesion with a score of 0 is symmetric in contour, color, and structure along both axes. A lesion is scored 1 point if there is asymmetry in contour, color, or structure in 1 axis, and 2 points if there is asymmetry in contour, color, or structure in both axes.
Fig. 5
Measuring asymmetry and border in the ABCD rule. When measuring asymmetry, the lesion is visually divided into two 90° axes. The axes should be oriented in a way that maximizes any existing symmetry ( A ). Borders are assessed by visually dividing the lesion into 8 segments and counting the number of segments that contain abrupt cutoff of pigment ( B ).
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Borders: the border score is determined by visually dividing the lesion into 8 sections (see Fig. 5 B). The pigment pattern of each wedge is assessed for abrupt cutoff at the margins, rather than a gradual thinning of pigment network. Border is scored by the number of segments of the lesion with a sharp demarcation, ranging from 0 to 8.
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Colors: the 6 colors that comprise the color score of a lesion are red, white, light brown, dark brown, blue-gray, and black. As discussed earlier, the dermatoscopic appearance of black, brown, gray, and blue-gray indicates the location melanin in the lesion. In addition, red usually indicates an inflammatory process, and white is seen with hyperkeratosis or scarring with regression. Color is scored by the number of these 6 colors present in the lesion, ranging from 1 to 6.
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Dermatoscopic structures: the dermatoscopic structure component is based on the presence of 5 specific structures, which include a pigment network, branched streaks, structureless or homogeneous areas, dots, and globules. The score is based on total number of different dermatoscopic structural components present in the lesion, ranging from 1 to 5.
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