INTRODUCTION — Dermoscopy is a noninvasive, in vivo technique primarily used for the examination of pigmented and nonpigmented skin lesions. Dermoscopy, dermatoscopy, epiluminescence microscopy, incident light microscopy, and skin-surface microscopy are synonyms. Dermoscopy is performed with a handheld instrument called a dermatoscope. The procedure allows for the visualization of subsurface skin structures in the epidermis, dermoepidermal junction, and superficial dermis; these structures are not visible to the naked eye [1-3].
Dermoscopic diagnosis involves the recognition of specific structures or their absence to confirm or rule out a given diagnosis. From a cognitive perspective, this task may be accomplished using a bottom-up or a top-down strategy. In the bottom-up approach, the observer performs a visual search for salient details (individual features) to arrive at a diagnosis, whereas in the top-down strategy the observer recognizes the general context, generates a hypothesis of the likely clinical diagnosis, and performs a targeted dermoscopic search for specific features to confirm the presumed clinical diagnosis [4].
This topic will review several algorithms and scoring systems that use mainly a top-down strategy to help clinicians distinguish melanocytic lesions from nonmelanocytic lesions (first step) and differentiate nevus from melanoma or lesions suspicious for melanoma (second step). The general principles of dermoscopy, dermoscopic structure terminology, dermoscopic evaluation of skin lesions, and the dermoscopic evaluation of facial, mucosal, and acral volar skin lesions are discussed separately. Dermoscopy of nail pigmentation and dermoscopic algorithms for skin cancer triage are also discussed separately.
●(See "Overview of dermoscopy".)
●(See "Dermoscopy of facial lesions".)
●(See "Dermoscopy of mucosal lesions".)
●(See "Dermoscopy of pigmented lesions of the palms and soles".)
●(See "Dermoscopy of nail pigmentations".)
●(See "Dermoscopic algorithms for skin cancer triage".)
THE TWO-STEP ALGORITHM FOR SKIN LESION EVALUATION — The two-step dermoscopy algorithm forms the foundation for the dermoscopic evaluation of skin lesions. It was introduced by the panel of the Consensus Internet Meeting on Dermoscopy in 2003 and has since undergone several modifications (algorithm 1) [5-7].
In the first step, the observer decides whether a lesion is melanocytic or nonmelanocytic by looking for the presence or absence of specific features. In addition to differentiating melanocytic lesions from nonmelanocytic lesions, the first step of the two-step algorithm also serves as an aid to correctly sub-classify the nonmelanocytic lesions [5,6]. (See "Overview of dermoscopy".)
The second step is intended only for lesions classified as melanocytic. Melanocytic lesions are further evaluated to differentiate nevi from suspicious lesions or melanoma by using one of several algorithms created for this purpose [8-12]. (See 'Second step: Nevus versus suspicious lesion or melanoma' below.)
FIRST STEP: MELANOCYTIC VERSUS NONMELANOCYTIC — One approach to differentiate melanocytic from nonmelanocytic lesions is based on an eight-level criterion ladder [6]. In this approach the observer evaluates the lesion for the presence or absence of specific dermoscopy criteria in an ordered sequence (figure 1).
The lesion is first examined for the presence of structures that are typical of melanocytic lesions. If none of those structures are found, the lesion is examined for the presence of features of dermatofibroma, basal cell carcinoma, squamous cell carcinoma, seborrheic keratosis, or angioma/hemangioma/angiokeratoma.
Lesions lacking features to classify them as one of the aforementioned categories are evaluated for the presence of blood vessels. The morphology, distribution, and arrangement of blood vessels can assist in classifying these lesions into melanocytic or nonmelanocytic tumors.
Lesions lacking features that would allow their characterization as melanocytic or nonmelanocytic lesions are classified as featureless (feature poor, nonspecific, nonclassifiable, or structureless) lesions. Melanoma needs to be ruled out for all featureless lesions. (See 'Featureless lesions (feature poor, nonspecific, nonclassifiable, or structureless)' below and 'Vascular structures in skin lesions' below.)
Criteria for melanocytic lesions — The structures that characterize melanocytic lesions include (figure 2 and picture 1A-C) [6,13] (see "Overview of dermoscopy", section on 'Colors and structures'):
●Pigment network
●Angulated lines
●Negative network
●Aggregated (three or more) or peripheral rim of globules
●Streaks (pseudopods and radial streaming)
●Homogeneous blue pigmentation
●Parallel pattern (for lesions on palm and soles)
●Pseudonetwork (facial skin)
Lesions presenting with any of the above structures are classified as melanocytic and will proceed to the second step to differentiate nevi from suspicious lesions or melanoma. (See 'Second step: Nevus versus suspicious lesion or melanoma' below.)
Exception to the rule: Dermatofibroma — While the presence of a network is indicative of a melanocytic lesion, there are exceptions. One such exception is exemplified by dermatofibroma, which is a nonmelanocytic lesion displaying a delicate pigment network at its perimeter with central scar-like area containing shiny white lines when seen with polarized light (picture 2) [14,15]. The delicate grid-like network in dermatofibroma often takes on the appearance of ring-like globules as it moves towards the central scar-like area. An additional clue to the diagnosis of dermatofibroma can be obtained by palpation, which will reveal a firm lesion that dimples inward when lateral pressure, directed towards the lesion, is applied at the lesion's edge (picture 3). (See "Overview of benign lesions of the skin", section on 'Dermatofibroma'.)
Criteria for basal cell carcinoma — The diagnostic criteria for basal cell carcinoma (BCC) include the lack of a pigment network and the presence of at least one positive feature for BCC (figure 3 and picture 4) [16]:
●Arborizing vessels
●Leaf-like areas
●Large blue-gray ovoid nests
●Multiple blue-gray, nonaggregated globules
●Spoke-wheel structures, including concentric globules
●Ulceration and small erosions
●Shiny white blotches and strands (seen with polarized dermoscopy) [17]
●Multiple in-focus, fine brown to gray dots
●Fine, short, superficial telangiectasias
Criteria for squamous cell carcinoma — The diagnostic criteria for squamous cell carcinoma (SCC) include (figure 4 and picture 5A-B) [18-20]:
●Glomerular vessels, usually focally distributed
●Rosettes
●White circles or keratin pearls
●Yellow scale
●Brown dots/globules aligned in straight, radially oriented lines, usually located towards the periphery
●Brown circles
Criteria for seborrheic keratoses — Most of the dermoscopic features of seborrheic keratoses are related to the papillomatous growth of the epidermis and the abundance of keratin in these tumors, and include (figure 5 and picture 6) [21]:
●Multiple milia-like cysts (three or more).
●Comedo-like openings.
●Moth-eaten borders.
●Gyri and sulci (also known as fissures and ridges) creating a cerebriform pattern. At times, these gyri and sulci can create a pattern resembling a network.
●Fingerprint-like structures.
●Hairpin vessels surrounded by a white halo.
Milia-like cysts can also be seen occasionally in other lesions such as BCCs and in melanocytic nevi, particularly in congenital nevi. Additional clues for seborrheic keratosis include sharp demarcation, network-like structure (due to pigment surrounding comedo-like and ostial openings), and a negative "wobble sign" [22]. The wobble sign allows differentiation of an epidermal keratinocytic lesion from a lesion with a dermal component such as a compound or intradermal nevus.
Criteria for hemangioma/angioma and angiokeratoma — Red, purple, or blue-black lagoons are the diagnostic criteria for hemangiomas/angiomas and angiokeratomas. They are small, well demarcated areas, often separated by septa, corresponding to dilated blood vessels in the dermis (picture 7).
Vascular structures in skin lesions — Both melanocytic and nonmelanocytic lesions can present as hypomelanotic or amelanotic lesions ("pink lesions") (picture 8A-B) [23]. The dermoscopic differentiation of such lesions can be challenging. Acknowledging the context of the lesion together with evaluating the morphology and architectural arrangement of vascular structures (picture 9) can provide clues to the correct diagnosis [24,25].
Comma-shaped, dotted, and linear irregular or serpentine vessels are usually seen in melanocytic lesions (table 1) [24]. Serpentine, dotted, or polymorphous vessels (two or more morphologies within the same lesion) are often seen in amelanotic melanomas. Dotted vessels can on occasion be seen in dysplastic and congenital nevi [26]. Thicker amelanotic melanomas may present a combination of dotted, serpentine, corkscrew, or arborizing vessels.
Regularly distributed hairpin vessels with a white halo are characteristic of seborrheic keratoses (picture 6), whereas arborizing vessels are typically seen in basal cell carcinomas (table 2 and picture 4).
Amelanotic or hypomelanotic lesions with atypical vascular morphology and/or arrangement should be biopsied to rule out amelanotic melanoma or other skin neoplasms (picture 9).
Featureless lesions (feature poor, nonspecific, nonclassifiable, or structureless) — Some skin lesions may not show any of the above criteria for melanocytic and nonmelanocytic lesions or may not display any vascular structures to assist in diagnosis. These lesions are defined as featureless (feature poor, nonspecific, nonclassifiable, or structureless) lesions (picture 10). Since a subgroup of melanomas may lack any recognizable dermoscopic structures, nonclassifiable lesions, especially if changing or symptomatic, should be biopsied to rule out melanoma.
SECOND STEP: NEVUS VERSUS SUSPICIOUS LESION OR MELANOMA — Once a lesion is classified as melanocytic, the observer proceeds to the second step, intended to differentiate nevus from suspicious lesions or melanoma [5]. The decision whether to reassure the patient, monitor the lesion, or perform a biopsy is based upon this second step. A small percentage of nonmelanocytic lesions may be misclassified as melanocytic in the first step. For example, some pigmented basal cell carcinomas may exhibit a dermoscopic pattern that raises suspicion of melanoma and a biopsy will be performed.
There are different algorithms and methods that aid the observer in the second step, including [2,8-12]:
●ABCD rule of dermoscopy (table 3)
●Menzies method (table 4)
●The seven-point checklist (table 5)
●Color, architectural disorder, symmetry, homogeneity/heterogeneity of dermoscopic structures (CASH) algorithm (table 6)
●Pattern analysis (table 7)
Although all methods have a similar sensitivity, pattern analysis has a superior specificity compared with the other quantitative scoring systems and is the method preferred by most experienced clinicians (table 8) [5,27]. Novices in dermoscopy will benefit from quantitative methods such as the dermoscopy ABCD rule, Menzies method, and the seven-point checklist, which are relatively simple, accurate, and reproducible [10,28,29].
Online tutorials on dermoscopy can be found at www.dermoscopedia.org, www.dermnetnz.org/doctors/dermoscopy-course/introduction.html or www.genomel.org/dermoscopy. Also, information regarding the two-step algorithm can be found in an app called Dermoscopy Two Step Algorithm.
ABCD rule of dermoscopy — The ABCD rule of dermoscopy is a semi-quantitative scoring system that employs four dermoscopic criteria to evaluate a pigmented lesion: asymmetry, border sharpness, colors, and dermoscopic structures (table 3) [8]:
●Asymmetry: Asymmetry refers to the contour and distribution of colors and structures within the lesion, in none, one, or two perpendicular axes (figure 6). The score for asymmetry ranges between zero and two points. The ABCD rule of dermoscopy and the CASH algorithm are the only algorithms that take into account both contour and distribution of colors and structures.
●Border sharpness: The border is evaluated for the presence of abrupt cutoffs between the lesion and the normal skin. The lesion is divided into a virtual pie with eight sections. For each segment presenting with an abrupt cutoff of pigment, a score of 1 is assigned. Hence, the border scoring ranges between zero and eight points.
●Colors: Presence of any of six colors within the lesion: white, red, light brown, dark brown, blue-gray, and black. The score for color ranges from one to six points.
●Differential dermoscopic structure: Presence of any of five structures including pigment network, homogeneous/structureless areas greater than 10 percent of the lesion (ie, hypopigmented or hyperpigmented blotches and depigmented or scar-like areas), branched streaks, dots, and globules. The score for dermoscopic structures ranges between one and five points.
The scores assigned to each feature are multiplied by a weighted factor and summed up in a final dermoscopy score. Sensitivity ranges from 78 to 90 percent and specificity from 45 to 90 percent among experts and non-experts [5,7,8,10,11,29-34].
Menzies method — The Menzies method was originally developed to differentiate invasive melanomas from other pigmented lesions (table 4) [35]. The method is based upon the evaluation of two negative features with a low sensitivity (0 percent) for melanoma, and nine positive features with a high specificity for melanoma (>85 percent).
"Negative features" are:
●Symmetry of the pigmentation pattern
●Presence of only one color (black, gray, blue, red, dark brown, or tan)
"Positive features" are:
●Blue-white veil
●Multiple brown dots
●Pseudopods
●Radial streaming
●Scar-like depigmentation
●Peripheral black dots/globules
●Broadened network
●Multiple blue/gray dots
●Multiple (five to six) colors
The presence of both negative features virtually excludes the diagnosis of melanoma. For all other lesions, the presence of any one of the positive features raises the suspicion for melanoma. Menzies method has a sensitivity of 85 to 92 percent and a specificity of 38 to 78 percent among examiners with various degrees of experience [5,7,11,30,33,35,36].
The seven-point check list — The seven-point checklist is based upon seven dermoscopic features frequently associated with melanoma (table 5) [10]:
Major criteria:
●Atypical pigment network
●Blue-whitish veil
●Atypical vascular pattern
Minor criteria:
●Irregular streaks
●Irregular dots/globules
●Irregular blotches
●Regression structures
A score is calculated by summing points allotted as two points for each of the major three criteria and one point for each of the four minor criteria. A final score of three or more suggests melanoma [10]. The seven-point checklist has a sensitivity of 62 to 95 percent and a specificity of 35 to 97 percent among experts and non-experts [5,7,10,30-32,34,35,37].
The presence of any one of the criteria has been proposed as sufficient to warrant a biopsy in a revised version of this check list [37]. This revised seven-point checklist lowered the threshold for biopsy, using a total score of one instead of three as sufficient to warrant a biopsy. Although this revision increased the sensitivity of the criteria, the authors acknowledge that the most sensitive and specific method to diagnose melanoma requires supportive evidence based on clinical characteristics, follow-up, and the comparative approach [38].
CASH algorithm — CASH is an acronym for Color, Architectural disorder, Symmetry, and Homogeneity/Heterogeneity of dermoscopic structures (table 6) [11].
This method is based upon evaluating a pigmented lesion for the following:
●Presence of few versus many colors
●Architectural order versus disorder
●Symmetry of shape and pattern versus asymmetry
●Homogeneity versus heterogeneity of dermoscopic structures
The scoring system for the CASH algorithm is shown in a table (table 6). A total CASH score of eight or more is suspicious of melanoma (range 2 to 17) [11]. A score of eight was chosen as a threshold that optimizes sensitivity and specificity for individuals with all levels of experience. However, a lower threshold for lesion excision may be appropriate for novices. The CASH algorithm has a sensitivity of 87 to 98 percent and a specificity of 67 to 68 percent [11,39].
Pattern analysis — Pattern analysis is based upon the association of an image with a recognition template developed from previous experience (table 7) [40,41]. It therefore requires the knowledge and recognition of the global and local patterns of nevi and melanoma [9,42,43]. For experienced clinicians, pattern analysis is a sensitive and specific method, whereas for nonexperts, it may have a worse diagnostic accuracy than the unaided eye [31,44].
In analyzing a melanocytic lesion using the pattern analysis method, it should be determined whether or not the lesion manifests one of the global patterns encountered in nevi. In broad terms, benign lesions have an organized distribution of dermoscopic structures, one or a few colors, and a symmetric pattern. In contrast, melanomas often have a disorganized distribution of structures, multiple colors, and an asymmetric pattern (figure 7).
Nevi: Global and local features — Nevi tend to manifest 1 of the 10 following benign global patterns (figure 8):
●Reticular diffuse: A diffuse pigment network composed of lines that have minimal variation in their color and thickness. The holes of the network also appear relatively homogeneous in size. The network tends to fade toward the periphery. This pattern is commonly seen in melanocytic nevi with a prominent junctional component (ie, junctional nevi, superficial congenital nevi) (picture 11).
●Reticular patchy: A subclassification of reticular diffuse and represents a reticular network similar to that described above presenting in focal patches that are distributed in a symmetric and organized manner. The patches are separated by homogeneous structureless areas, which are of the same color or slightly darker than the background skin. This pattern is commonly seen in acquired melanocytic nevi and superficial congenital nevi (picture 12).
●Peripheral reticular with central hypopigmentation: A uniform network at the periphery of the lesion with a central homogeneous and hypopigmented structureless area. The structureless area has the same color, or slightly darker as compared to the background skin. This pattern is commonly seen in acquired melanocytic nevi, especially in individuals with fair skin (picture 13).
●Peripheral reticular with central hyperpigmentation: A uniform network at the periphery of the lesion with a central homogeneous and hyperpigmented structureless area or blotch. This pattern is commonly seen in acquired melanocytic nevi, especially in individuals with darker skin (picture 14).
●Homogeneous pattern: A diffuse homogeneous structureless pattern in a stable and non-changing lesion. It may appear as gray-blue as seen in blue nevi, brown as seen in congenital nevi, or tan-pink as seen in acquired nevi in individuals with fair skin (picture 15).
●Peripheral reticular with central globules: A uniform network at the periphery of the lesion with central globules. This pattern is commonly seen in congenital nevi (picture 16).
●Peripheral globules with central network or homogeneous area, including the starburst pattern: The central component consists of a reticular or homogeneous pattern. The peripheral component can manifest in one of three ways: a single row of globules as seen in some actively growing nevi; more than one row of globules (ie, tiered globules) creating a starburst pattern as commonly seen in Spitz nevi; and streaks (classic starburst pattern) giving the appearance of an exploding star, as seen in Spitz/Reed nevi (picture 17).
●Globular pattern: Globules of similar shape, size, and color are distributed throughout the lesion. Globules may be large and angulated, creating a cobblestone pattern as seen in dermal nevi and some congenital nevi (picture 18).
●Two-component pattern: A combination of two patterns with one half of the lesion manifesting one pattern and the other half another pattern. The most common two-component pattern is the reticular-globular pattern (picture 19).
●Multicomponent pattern: A combination of three or more patterns distributed symmetrically in at least one axis (picture 20).
Nevi on volar surfaces present a parallel furrow pattern or another of the benign patterns. The parallel furrow pattern is characterized by the presence of pigment along the sulci (furrows) of palms and soles (picture 21). (See "Dermoscopy of pigmented lesions of the palms and soles".)
After determining whether or not the lesion adheres to 1 of the 10 benign global patterns, the observer proceeds to analyze the lesion's local features. A description of the typical and atypical variants of the local features with their diagnostic associations is provided in the table (table 7).
Melanoma: Global and local features — The melanoma specific structures are, by convention, termed atypical/irregular. Many of these atypical/irregular structures have a typical/regular counterpart that is associated with nevi (table 7).
Global features of melanoma are:
●Deviation from the benign patterns and at least 1 of the 10 melanoma specific structures.
●Multicomponent pattern: A combination of three or more patterns (eg, reticular, globular, and homogeneous), asymmetrically distributed in the lesion. It has also been defined as a lesion with three or more dermoscopic structures distributed asymmetrically.
●Nonspecific pattern: Lack of any recognizable global pattern of pigmentation.
●Volar skin patterns: Melanomas on palms and soles (ie, volar surfaces) can present with a multicomponent pattern, nonspecific pattern, or a parallel ridge pattern, which is characterized by the presence of pigment along the cristae (ridges) of palms or soles. (See "Dermoscopy of pigmented lesions of the palms and soles".)
●Facial skin patterns: Lesions on facial skin can present with a multicomponent pattern, nonspecific pattern, asymmetric follicular openings, perifollicular granularity, circle within a circle, angulated lines creating zigzag lines or coalescing to form polygons such as rhomboidal structures, and blotches obliterating follicular openings.
Lesions displaying a multicomponent or nonspecific pattern are further examined for the following 10 melanoma specific structures (picture 22A-D):
●Atypical network, including angulated lines.
●Peripheral streaks (pseudopods and radial streaming).
●Negative network.
●Off-centered blotch.
●Atypical dots and/or globules.
●Regression structures, including granularity (also known as peppering), and scar-like areas. The presence of granularity and scar-like areas within the same lesion result in the appearance of a blue-white coloration, usually overlying macular areas.
●Blue-white veil overlying raised areas.
●Atypical vascular structures.
●Shiny, white lines (formerly known as crystalline structures).
●Tan peripheral structureless areas.
The sensitivity, specificity, and predictive value of melanoma specific structures are provided in the table (table 9).
A lesion is considered malignant if it deviates from the benign patterns, and has at least 1 of the 10 melanoma-specific structures. Lesions are considered suspicious if they have a benign pattern and reveal a melanoma specific structure, or if they do not adhere to one of the benign global patterns and lack a specific feature of melanoma.
DERMOSCOPY FROM A MANAGEMENT PERSPECTIVE — The primary purpose of examining a skin lesion with a dermatoscope is to determine whether the lesion should be biopsied or not [45]. The decision to biopsy a suspicious lesion should be based upon the combination of clinical and dermoscopic examination of the lesion in question as well as surrounding lesions (comparative approach) and other relevant information (ie, context), including history of change, associated symptoms, skin type, location, and personal and family history of melanoma and other skin cancers.
In patients with multiple nevi, it is useful to identify the "signature nevus" pattern (the predominant type of nevus) as well as lesions that deviate from the predominant pattern ("ugly duckling" lesions), both clinically and dermoscopically [46,47]. A comparative dermoscopic approach to the patient with multiple nevi reduces the number of excisions of benign nevi [48]. (See "Melanoma: Clinical features and diagnosis", section on 'The "ugly duckling" sign'.)
After a complete clinical and dermoscopic examination utilizing the two-step dermoscopy algorithm, a management decision can be rendered (algorithm 1):
●If the lesion is considered to be benign, the patient can be reassured, educated on the importance of self-skin examination, and instructed to return if changes are detected [49,50].
●If the lesion is considered to be a melanoma, it should undergo excisional biopsy [51-54].
●If the lesion is considered suspicious, there are two options: perform a biopsy or refer the patient to an expert clinician for further evaluation.
The management decision will depend on several factors such as the pretest probability of the diagnosis of the lesion. For example, a lesion with a spitzoid morphology in a child is less likely to be a melanoma than a similar lesion in an adult. Based on the pretest probability, the clinician may be more likely to biopsy spitzoid lesions in adults than in children. Other factors that may influence the management decision include whether or not the lesion is an isolated lesion or one in a sea of many nevi, and whether or not the lesion is a clinical or dermoscopic outlier lesion.
Lesions referred to an expert for further evaluation may be deemed benign, biopsied, or subjected to short-term monitoring. The rationale behind short-term monitoring is that stable lesions are biologically indolent and represent nevi, whereas changing lesions are biologically dynamic and may be atypical nevi or melanoma [55,56].
Short-term dermoscopic monitoring, which consists of comparing digital dermoscopic images of the same lesion taken approximately three to four months apart, should ideally be performed in specialized centers by experienced clinicians [55-57]. This type of monitoring is only suitable for macular (nonpalpable) lesions; suspicious or atypical nodular (palpable) lesions should be biopsied.
Short-term dermoscopic monitoring is a safe and accepted approach to monitor these flat (nonpalpable) atypical lesions. In one study, 19 percent of 318 nevi showed a change during this time period (2.5 to 4.5 months) and 11 percent of those changing lesions were found to be early melanomas [55].
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Dermoscopy".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Seborrheic keratosis (The Basics)")
SUMMARY AND RECOMMENDATIONS
●The two-step dermoscopy algorithm forms the foundation of the dermoscopic evaluation of skin lesions. It is based upon the systematic search and recognition of specific dermoscopic structures to distinguish melanocytic and nonmelanocytic lesions, diagnose common benign and malignant nonmelanocytic lesions, and decide whether a melanocytic lesion is benign, suspicious, or malignant. (See "Overview of dermoscopy", section on 'Colors and structures'.)
●In the first step the observer decides whether a lesion is melanocytic or nonmelanocytic by looking for the presence or absence of specific features. (See 'Criteria for melanocytic lesions' above.)
●Nonmelanocytic lesions are further examined for the presence of features of dermatofibroma, basal cell carcinoma, squamous cell carcinoma, seborrheic keratosis, angioma, or other benign or malignant nonmelanocytic lesions. The possibility of a featureless or amelanotic melanoma should be kept in mind. (See 'Criteria for basal cell carcinoma' above and 'Criteria for seborrheic keratoses' above and 'Criteria for hemangioma/angioma and angiokeratoma' above and 'Vascular structures in skin lesions' above.)
●In the second step of the two-step algorithm, melanocytic lesions are further evaluated to differentiate benign nevi from suspicious lesions or melanoma. The decision whether to reassure the patient, monitor the lesion, or perform a biopsy is based upon this second step. (See 'Second step: Nevus versus suspicious lesion or melanoma' above.)
●The second step is performed using one of several algorithms. Clinicians with limited experience in dermoscopy may benefit from quantitative methods, such as the ABCD rule, Menzies method, and the seven-point checklist. These methods are relatively simple, accurate, and reproducible. (See 'ABCD rule of dermoscopy' above and 'Menzies method' above and 'The seven-point check list' above and 'CASH algorithm' above and 'Pattern analysis' above.)
●If a lesion is considered to be benign after a thorough clinical and dermoscopic examination, the patient can be reassured and educated on the importance of self-skin examination and instructed to return if changes occur. If the lesion is considered suspicious, there are two options: perform a biopsy or refer the patient to an expert clinician for further evaluation. Lesions referred to an expert for further evaluation may be deemed benign, biopsied, or subjected to short-term dermoscopic monitoring. (See 'Dermoscopy from a management perspective' above.)
●If the lesion is considered to be a melanoma, it should undergo excisional biopsy. (See "Melanoma: Clinical features and diagnosis", section on 'Biopsy'.)
