|Dermoscopy: A Literature Review
Dalia Hossam, Ahmed Sadek, Nehal Saied
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Dermoscopy is a surface skin microscopy technique that rapidly grew during the past years enhancing the non invasive dermatological diagnostic techniques effectively. Its main applications include classic dermoscopy, trichoscopy, entomodermoscopy, inflammoscopy, capillaroscopy and dermoscopy for treatment decision and monitoring.
Dermoscopy is a non-invasive technique that allows a rapid and magnified in vivo observation of the skin with the visualization of morphologic features invisible to the naked eye 
(I) Classic dermoscopy
It aids in the diagnosis of pigmented and non-pigmented skin tumors including melanocytic, non-melanocytic, benign, and malignant skin tumors. There are two major approaches; the Heuristic approach and the Analytical approach. The Heuristic approach is called "The Pattern Analysis" and utilizes a 2 step algorithm (Fig 2). In the first step of decision making, the physician decides whether a lesion is of melanocytic or non-melanocytic origin through the following seven steps 
- Level 1: Criteria of Melanocytic Lesions
The lesion is considered of melanocytic origin if any structure of the following is present; pigment network (Fig 3.a), branched streaks (Fig 3.b), streaks, negative network (Fig 3.c), aggregated globules (Fig 3.d), homogenous blue pigmentation (Fig 3.e), pseudo-network (face) (Fig 3.f), or parallel pattern (palms, soles, and mucosa) (Fig 4).
Diagnosing the lesion as pigmented in origin allows the physician to proceed to step two to evaluate whether it is benign, suspicious, or malignant.
Dermatofibroma can be also diagnosed at this level, characterized by multiple patterns, the most common of them is a central white structureless area surrounded by fine peripheral pigment network.
- Level 2: Criteria for basal cell carcinoma
Search for the presence of specific morphologic criteria for basal cell carcinoma which include arborizing blood vessels, leaf-like areas, large blue-gray ovoid nests, multiple blue-gray non-aggregated globules, spoke-wheel-like structures, shiny white areas, or ulceration (Fig 5). 
- Level 3: Criteria for seborrheic keratoses
Look for multiple milia-like cysts, comedo-like openings, crypts, moth-eaten borders, network-like structures, "fissures and ridges" that sometimes give a brain-like or cerebriform appearance to the lesion, fat finger like structures), or light brown fingerprint-like structures (Fig 6).
- Level 4: Criteria for vascular lesions
The presence of red, maroon, or red-blue to black lacunae (also known as lagoon-like structures), indicates that the lesion is a haemangioma or angiokeratoma (Fig 7).
- Level 5: Specific blood vessels in non-melanocytic lesions
If none of the morphologic criteria described in the previous levels can be identified, then the lesion is considered amelanotic or hypomelanotic. In such lesions, the physician may be able to find vascular structures that can assist in the diagnosis. It is important to observe both the morphology and distribution of the vessels. Hairpin vessels surrounded by a whitish halo is a characteristic of keratinizing tumors, such as keratoacanthoma and seborrheic keratosis (Fig 8a). The presence of glomerular vessels, usually aggregated focally at the periphery of the lesion identifies the lesion as a squamous cell carcinoma or bowen's disease (Fig 8b). The presence of blood vessels arranged like "string of pearls" is a hallmark of clear cell acanthoma (Fig 8c) while the presence of crown vessels identifies the lesion as a sebaceous hyperplasia or molluscum contagiosum (Fig 8d) 
- Level 6: Specific blood vessels in melanocytic lesions
The presence of predominantly comma shaped blood vessels is a hallmark of intradermal nevi. The blood vessel morphology encountered in melanoma includes dotted (Fig 9a), linear irregular (Fig 9b), atypical hairpin (serpentine) vessel in a pink background, and cork screw (Fig 9c), tortuous vessels or milky red areas (Fig 9d) . If more than one type of vessel morphology is seen within the same lesion, the vascular pattern is termed "polymorphous" (Fig 9e), which is the most common pattern associated with melanoma. Lesions that do not display any of the structures mentioned in steps 1-6 are considered "structureless" and for such lesions one needs to proceed to level 7 (Fig 10) 
- Level 7: "Structureless" lesions
This category includes all lesions that fail to reveal any specific diagnostic structures to help classify them as melanocytic or as one of the non-melanocytic lesions. For example, the presence of fine dots, peppering, blue white veil, crystalline structure, and blotches may be present in these lesions. Although these structures cannot be used to differentiate melanocytic from non-melanocytic lesions, they can be clues that aid in correctly identifying melanomas and some basal cell carcinomas. These lesions either should be biopsied or should be subjected to short-term mole monitoring in an attempt to ascertain their biologic behavior 
The second step of decision making is deciding whether the melanocytic lesion is benign, suspect or melanoma. To accomplish this, many different approaches have been proposed.
Revised 7- point checklist (Fig 11) 
The seven-point checklist is based on the detection of seven dermoscopic features commonly associated with melanoma
A score is calculated by summing points giving one point for each criterion. If the lesion scores 1 or more, then it should be examined carefully as it's suspicious for melanoma.
Three-Point Checklist 
The presence of more than one of the above three criteria is suggestive of
a malignancy (basal cell carcinoma or melanoma).
Pattern analysis 
Benign nevus patterns include: (Fig 12)
Melanoma specific features include: (Fig 13)
Revised pattern analysis  (Analytical approach)
Basic Elements (Fig 14)
All patterns observed in dermoscopy are composed of
five simple geometric elements. These basic elements are:
Patterns Formed by Basic Elements (Fig 15,16)
A pattern is built up of multiple repetitions of the same single basic element. There is also a pattern "structureless," an area characterized by the absence of any of the basic elements, or at least with no basic element dominating. Lines can be arranged to form five different patterns: reticular, branched, parallel, radial, and curved.
Colors seen in dermoscopy are created by various combinations of keratin, melanin, blood (including serum in crusts), collagen, and foreign material. The color of melanin varies greatly depending on localization in the epidermis or dermis (Fig 17).
Morphology: (Fig 18)
Distribution (Fig 19)
The analytical approach is based on the Chaos & Clues method, any pigmented skin lesion is then classified into either chaotic or not based on its color, pattern but not on outline or shape. If the lesion is not chaotic, then no further intervention is needed, but if chaotic then, you should search for a clue for the diagnosis of melanoma which are:
The only exceptions for this rule is the growing nodules in adults as well as facial lesions with any grey colour and acral volar lesions with parallel ridge pattern.
ABCD rule (Table 1) 
Menzies method 
To diagnose melanoma, both of the following negative features must not be found: a single color or point and axial symmetry of pigmentation. Additionally, at least one positive feature of the following must be found; blue-white veil, multiple brown dots, pseudopods, radial streaming, scar-like depigmentation, peripheral black dots or globules, multiple colors (5 or 6), multiple blue/gray dots or broadened network.
(II) Trichoscopy: 
It is that branch of dermoscopy dealing with hair and scalp disorders. It is rapidly gaining acceptance in the diagnosis and follow up treatment of cicatricial and non cicatricial alopecias. It can be used also in diagnosing different hair shaft disorders as well as infections and infestations.
Non- cicatricial alopecia: (Fig 20, 21)
The hallmark trichoscopic features of alopecia areata are regularly distributed yellow dots, micro-exclamation mark hairs, tapered hairs, black dots, broken hairs, and upright and regularly coiled (circle, pigtail) re-growing hairs. Trichorrhexis nodosa may be observed, especially in active, early alopecia areata. It must be emphasized that micro-exclamation mark hairs are not pathognomonic for alopecia areata. Trichoscopy of alopecia areata may differ depending on the disease activity, severity and duration.
Table 2: Trichoscopic features of alopecia areata
Male and female AGA share similar trichoscopic features, including hair shaft thickness heterogeneity, thin hairs, yellow dots, perifollicular discoloration (the peripilar sign), an increased proportion of vellus hairs, and a large number of follicular units with only one emerging hair shaft. Thin wavy hair and honeycomb hyperpigmentation often coexist as additional, unspecific features. These features are more pronounced in the frontal compared to the occipital region.
Trichoscopy has limited value in diagnosing telogen effluvium. Frequent, but not specific, findings include the presence of empty hair follicles, a predominance of follicular units with only one hair, perifollicular discoloration (the peri-pilar sign), and upright re-growing hairs with lack of features of any other disease. There is no significant difference between the findings in the frontal area and those of the occipital area, which differentiates telogen effluvium from androgenetic alopecia.
Trichoscopy of trichotillomania is characterized by a chaotic pattern of diverse features related to hair fracturing. The most characteristic features are hairs broken at different lengths, short hairs with trichoptilosis (split ends), irregular coiled hairs, amorphous hair residues, and black dots.
Dermoscopy of tinea capitis shows two typical features; comma hairs (curved fractured hair shafts) and corkscrew hairs. Broken and dystrophic hairs also are seen.
Cicatricial alopecias (Fig 22)
Trichoscopic features of active lesions include; perifollicular scaling (scales entangling hair shafts up to 2-3 mm above the scalp surface in a tubular manner), hair casts, elongated linear blood vessels and violaceous areas. Inactive lesions show irregular, large white dots (fibrotic white dots), white areas, milky red areas (strawberry ice cream color) and tufted hairs.
Frontal fibrosing alopecia
Scalp lesions show lack of follicular openings, homogenous ivory-colored background, minor perifollicular scaling, perifollicular erythema, follicular openings with only one hair at the hair-bearing margin, perifollicular brown or brown-violet areas (in dark-skinned patients). While eyebrows lesions show multiple regularly distributed red dots in early phase of disease and multiple regularly distributed red or gray to gray-brown dots in advanced cases.
Discoid lupus erythematosus
Active (early) lesions show thick arborizing vessels, large yellow dots corresponding to the follicular keratotic plugs, fine interfollicular scaling, scattered brown discoloration, red dots, blue-gray dots (on dark or sun-exposed skin). On the other hand, inactive (end-stage) lesions show loss of follicular openings, pink areas, white areas, arborizing vessels and yellow dots containing thin spider vessels (in prefibrotic lesions).
Active disease show tufts of five or more hairs in one follicular unit, yellow follicular pustules, yellowish tubular scaling with collar formation, yellow discharge, starburst sign corresponding to folds of epidermal hyperplasia with elongated looped or coiled vessels arranged in concentric perifollicular pattern. Late stage (inactive disease), milky red areas lacking follicular openings or white areas lacking follicular openings are usually seen.
Trichoscopic features of active dissecting cellulitis include; yellow structureless areas, yellow 3D (soap bubble) dots with or without hair shafts, black dots, pinpoint-like vessels with a whitish halo, cutaneous clefts with emerging hairs and hair tufts.
Pseudopelade of Brocq
Trichoscopic features of pseudopelade of Brocq include; no follicular openings, smooth white areas, dystrophic hairs at the periphery of the lesion with no features indicative of other types of cicatricial alopecia.
Hair shaft abnormalities
They can also be seen as in cases of fractured hair in the form of: trichoptilosis, trichoschisis/trichoclasis and Irregular fractures caused by mechanical force or trichorrhexis invaginata, narrowing as in cases of monilethrix, monilethrix-like congenital hypotrichosis, monilethrix-like hairs (Pohl-Pinkus constriction), pseudomonilethrix, tapered hairs and exclamation mark hairs, node-like appearance as in cases of trichonodosis, trichorrhexis nodosa, Bamboo hairs (trichorrhexis invaginata) and hair casts, curls and twists as in pigtail hairs (circular or oval), coiled hairs, comma hairs, corkscrew hairs, z-hairs (zigzag hairs), pili torti or woolly hairs, bands as in cases of interrupted medulla, pili annulati and interrupted (Morse code-like) hairs and short hairs as in cases of upright re-growing hairs, vellus hairs, tulip hairs, block hairs, i-hairs, broom hairs and flame hairs.
It is the one diagnosing skin infections and infestations
This is the one involved with inflammatory skin diseases.
Fig 24: Different types of inflammatory skin diseases detected by dermoscopic examination A,B,C,D 
It evaluates the nail fold capillaries for the screening of autoimmune diseases.
Fig 25 : Dermoscopic examination of nail fold capillaries in scleroderma patient showing enlarged capillary loops with hemorrhage 
(VI) Dermoscopy for treatment decision and monitoring: 
It is used for taking decisions preoperatively regarding lesions margins and extension, and in follow up especially after non-invasive treatment modalities.
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