INTRODUCTION
Dermoscopy or dermatoscopy is a noninvasive technique of mucocutaneous examination with an instrument known as the dermoscope or dermatoscope.1 The dermoscope has a magnified lens with a polarized/nonpolarized or dual light source which can visualize superficial and deeper layers of skin yielding a better insight into the morphology and pathology of a condition.
A BRIEF HISTORY
Advent of dermoscopy started as early as 1655 when a French doctor, Pierre Borel pioneered the use of microscope to observe capillaries on the nail bed. Johan Kolhaus, Ernst Abbe, and Karl Heuter are the other pioneers in this field.2 Johann Saphier, who is attributed with describing pigment globules, and using the term “dermatoscopy” in 1920s, is considered the father of dermoscopy,3 and Leon Goldman is credited with the use of term “dermoscopy”.4 In 1970, Saitoh et al. initiated trichoscopy.5
In 1981, Fritsch and Pechlaner characterized the pigmented network.6 Pehamberger et al. introduced pattern analysis in pigmented lesions in 1987.7 In 1989, the first Consensus Conference on Skin Surface Microscopy (Hamburg, Germany) defined criteria for dermoscopy. Soyer et al. established a correlation between dermoscopic and histopathologic structures.8
In 1989, the first dermoscope consisting of halogen light with 10X magnification was marketed as DELTA 10. Application of immersion oil to skin surface aiding translucency was described in 1989 by Wilhelm Stolz et al.9
In 1994, the ABCD rule of dermoscopy was published by Wilhelm Stolz.10 In the same year, Binder et al. used dermoscopic images to train an artificial neural network in differentiating melanomas from melanocytic nevi.11 In 1997, MoleMax, the first dermoscopy system was released by Derma Medical Systems Company in cooperation with department of Dermatology of Medical University of Vienna.
In 2000, a virtual Consensus Net Meeting on Dermoscopy refined dermoscopic terminology and validity of various dermoscopic criteria and diagnostic algorithms.12
At the meeting of the American Academy of Dermatology in 2001 at Washington, DC, the World's first polarized pocket dermoscope—DermLite DL100 by 3Gen company was launched. HAM10000 (Human Against Machine with 10000 training images) dataset is a large collection of multi-source dermoscopic images of common pigmented skin lesions.13
CONCEPT OF DERMOSCOPY
Dermoscope works on the principle that transillumination of a lesion at higher magnification will reveal subtle variations in texture, color, and pattern of skin surface and subsurface lesions, thereby helping to delineate changes better as the light is absorbed and reflected by different skin surface components.14
The basic concepts of dermoscopy including pattern recognition, various algorithms, and steps and description of various terminologies will be covered in subsequent chapters.
STRUCTURES THAT CAN BE VISUALIZED
These include melanin, hemoglobin, keratin, collagen, follicular structures, eccrine gland openings, and vessels. Glandular concretions, pigment network and its variations, scar tissue, scaling, foreign particles, hair follicle and shaft, nail fold and its capillary network, and cuticle are also better delineated by dermoscopy.15
Normal skin is visualized as homogeneous pigment network which consists of darker reticulate lines with paler 2areas of pigmentation in between that make a grid pattern. The darker lines correspond to melanin in the vertical stem of rete ridges and paler hypopigmented areas are due to melanin in the horizontal stem of rete ridges.16 Melanocytic pigmentation has characteristic appearance including: reticular pigment network, structureless pigment areas, dots, and globules. In addition, acral areas have parallel furrow, lattice, and fibrillary pattern.17 The common morphological types of vascular structures include dotted, comma-like, linear, hairpin, glomerular, and arborizing vessels.18
Color variation: Though eumelanin is brown in color, Tyndall effect leads to color variegation depending upon the location and density of pigmentation which is of diagnostic significance.19 The details of color variegation are depicted in Table 1.
Mucosa
Lesions located in accessible mucocutaneous areas like eyelids, lips, anogenital region, accessible part of oral mucosa are amenable to dermoscopy. Plastic food wraps or ice caps can be used to limit direct contact with the lens.20 Pigment network is not seen in mucosae as rete ridges are absent. Mucosal pigmentation, benign and malignant tumors, inflammatory conditions can be identified.20
Hair
Trichoscopy is useful to visualize alopecia, scarring, variations in hair follicle, follicle unit, hair shaft anomalies, scalp pigmentation, scaling, vasculature, infections like piedra and pediculosis. Various descriptive terms are used which will be elaborated upon in coming chapters.
Nail
Normal nail fold capillary loops are placed at regular intervals and are thin, hairpin-like and of uniform diameter. Nail fold capillaroscopy is widely used in various connective tissue diseases.21 Onychoscopy also assists in the visualization of the cuticle, lunula, nail plate, changes in the nail bed, free edge of nail plate, and hyponychium and onychomycotic changes.
Dermoscopy is a constantly upgrading diagnostic methodology based on algorithms and diagnostic criteria, which are frequently being put forth and refined.24
Common dermatological uses include:
- Differentiating melanocytic and nonmelanocytic lesions like nevi, seborrheic keratosis, lentigines, pigmented basal cell carcinoma, and dermatofibroma.
- Dermoscopy enhances diagnostic sensitivity of melanoma to 85% from the usual 65–80%.
- Confirming diagnosis of ectoparasitic infestations like scabies, pediculosis, tungiasis, and Demodex folliculitis.
- Differentiating between various alopecias (cicatricial vs. noncicatricial).
- The diseases which can be diagnosed by dermoscopy are continually increasing in number and are shown in Table 2.
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- Disease activity evaluation: Alopecia areata, vitiligo, frontal fibrosing alopecia, skin tumors.
- For patient reassurance and follow-up of lesions at regular intervals.
- Wart mapping in areas like beard, face, even for genital warts to assess the extent of warts for treatment purpose.
- To detect intra- and subcutaneous foreign bodies like glass shards, suture bits, grit.
- For better and early visualization of adverse effects of topical corticosteroids.
- To define the exact surgical excision margin for skin tumors.
- Dermoscopy guided biopsy: For more accurate histopathological diagnosis.
- Dermoscopy is used in clinical studies as accurate measures of pre- and postinterventional changes.
- In evaluating efficacy of laser hair reduction.
- Dermoscopy in hair transplant: To assess the number and size of hair follicle units, and to diagnose early post-transplant folliculitis.
- Confirmation of imperceptible findings in skin tests like pathergy, patch test, and intradermal tests.
ADVANTAGES OF DERMOSCOPY
Dermoscopy aids in:27
- Digital surveillance and monitoring of melanocytic lesions.
- Valuable in assessing pigmented and nonpigmented skin tumors and atypical and dysplastic nevi.30
- Monitoring the results of tumor treatment and is an assisting tool in tumor surgery.31
- Onychoscopy is helpful in evaluating nail disorders and in differentiating neoplastic and non-neoplastic diseases.31
- Entomodermoscopy is an effective and sensitive tool in diagnosis of viral, fungal, and parasitic diseases.31
- Trichoscopy is useful in detecting various alopecias and inflammatory scalp diseases and in monitoring and follow-up.
LIMITATIONS OF DERMOSCOPY32
- Adequate training and expertise is needed for dermoscopic analysis.
- Instruments are relatively expensive.
- The findings are subject to the light, type of dermoscope, and camera being used, also on application pressure and contact or noncontact method.22
- Dermoscopy has limited role in the diagnosis of very early and mainly featureless melanomas.33
- Anchoring bias: Diagnosis is based on a single dermoscopic finding.
- Search satisfaction: Tendency to fix the diagnosis based on partial information and not probing further.27
- In contact dermoscopy, faceplate of dermoscope needs to be disinfected before using in next patient.25
- Artifacts like colored powders, dust, dye, cosmetics can hinder proper visualization and cause confusion.
- Different dermoscopes yield different magnification and color grades, which lead to lack of uniformity.
FUTURE OF DERMOSCOPY
Dermoscopy is evolving into subcategories like pigmenteroscopy, inflammoscopy mucoscopy, and entodermoscopy.26 The future trend is the use of artificial intelligence and teledermoscopy. Teledermoscopy and skin health self-inspection will become a new trend with the development of dermoscopic image analysis technology which will improve diagnostic accuracy.34
Artificial Intelligence
There is tremendous improvement in technology with periodic launch of newer and better handheld as well as videodermoscopy devices.
KEY POINTS
- First commercial dermoscope was manufactured in 1989.
- Various steps, algorithms, and pattern recognitions are set for diagnostic uniformity of conditions by dermoscopy.
- Dermoscopy now embraces various subcategories like trichoscopy, onychoscopy, mucoscopy, inflammoscopy, and entodermoscopy.
- It is used not only in diagnosis, but also in treatment monitoring, side effects of treatment, and for marking areas for biopsy and excision.
- Teledermoscopy is in the near future.
CONCLUSION
Dermoscopy, the method of noninvasive visualization of skin structures, is a helpful tool in the diagnosis and differentiation of many dermatoses. Trichoscopy is most evidence-based science of dermoscopy whereas onychoscopy is still evolving. Further research is recommended in the field of dermoscopy for validation of certain patterns.
- Ackerman AB. Dermatoscopy, not dermoscopy! J Am Acad Dermatol. 2006;55:728.
- Domínguez-Espinosa AE. History of dermoscopy. Dermatol Rev Mex. 2014;58:165–72.
- Berk-Krauss J, Laird ME. What's in a name-dermoscopy vs dermatoscopy. JAMA Dermatol. 2017;153:1235.
- Goldman L. Some investigative studies of pigmented nevi with cutaneous microscopy. J Invest Dermatol. 1951;16:407–26.
- Kharkar V. Overview of trichoscopy. In: Khopkar US (Ed). Dermoscopy and Trichoscopy in Diseases of the Brown Skin: Atlas and Short Text. New Delhi: Jaypee Brothers Medical Publishers (P) Ltd; 2012. pp. 167–81.
- Fritsch P, Pechlaner R. Differentiation of benign from malignant melanocytic lesions using incident light microscopy. In: Ackerman AB, Mihara I (Eds). Pathology of Malignant Melanoma. New York: Masson; 1981. pp. 301–12.
- Pehamberger H, Steiner A, Wolff K. In vivo epiluminescence microscopy of pigmented skin lesions. I. Pattern analysis of pigmented skin lesions. J Am Acad Dermatol. 1987;17:571–83.
- Bahmer FA, Fritsch P, Kreusch J, Pehamberger H, Rohrer C, Schindera I, et al. Terminology in surface microscopy. Consensus meeting of the Committee on Analytical Morphology of the Arbeitsgemeinschaft Dermatologische Forschung, Hamburg, Federal Republic of Germany, Nov. 17, 1989. J Am Acad Dermatol. 1990;23:1159–62.
- Stolz W, Bilek P, Landthaler M, Merkle T, Braun-Falco O. Skin surface microscopy. Lancet. 1989;2:864–5.
- Stolz W, Riemann A, Cognetta AB. ABCD rule of dermatoscopy: a new practical method for early recognition of malignant melanoma. Eur J Dermatol. 1994;4:521–7.
- Binder M, Steiner A, Schwarz M, Knollmayer S, Wolff K, Pehamberger H. Application of an artificial neural network in epiluminescence microscopy pattern analysis of pigmented skin lesions: a pilot study. Br J Dermatol. 1994;130:460–5.
- Argenziano G, Soyer HP, Chimenti S, Talamini R, Corona R, Sera F, et al. Dermoscopy of pigmented skin lesions: results of a consensus meeting via the Internet. J Am Acad Dermatol. 2003;48:679–93.
- Tschandl P, Rosendahl C, Kittler H. The HAM10000 dataset, a large collection of multi-source dermatoscopic images of common pigmented skin lesions. Sci Data. 2018;5:180161.
- Nirmal B. Dermatoscopy: physics and principles. Indian J Dermatopathol Diagn Dermatol. 2017;4:27–30.
- Witkowski A, Pellacani G, Gonzalez S, Longo C. Dermoscopy: basic knowledge of an innovative imaging tool. In: Humbert P, Fanian F, Maibach H, Agache P (Eds). Agache's Measuring the Skin. Cham: Springer Nature; 2017. pp. 211–28.
- Nischal KC, Khopkar US. Principles and technique of dermoscopy and videodermoscopy. In: Khopkar US (Ed). Dermoscopy and Trichoscopy in Diseases of the Brown Skin: Atlas and Short Text. New Delhi: Jaypee Brothers Medical Publishers (P) Ltd; 2012. pp. 1–9.
- Rosendahl C, Cameron A, McColl I, Wilkinson D. Dermatoscopy in routine practice—'chaos and clues'. Aust Fam Physician. 2012;41:482–7.
- Ayhan E, Ucmak D, Akkurt Z. Vascular structures in dermoscopy. An Bras Dermatol. 2015;90:545–53.
- Weismann K, Lorentzen HF. Dermoscopic color perspective. Arch Dermatol. 2006;142:1250.
- Blum A, Simionescu O, Argenziano G. (2021). Dermoscopy of mucosal lesions. [online] Available from https://www.uptodate.com/contents/dermoscopy-of-mucosal-lesions [Last accessed October, 2021].
- Jadhav P, Khopkar US. Nail fold capillaroscopy in connective tissue disorders. In: Dermoscopy and Trichoscopy in Diseases of the Brown Skin: Atlas and Short Text. Khopkar US (Ed). New Delhi: Jaypee Brothers Medical Publishers (P) Ltd; 2012. pp. 157–68.
- Haldar SS, Nischal KC, Khopkar US. Dermoscopy: applications and patterns in diseases of the brown skin. In: Dermoscopy and Trichoscopy in Diseases of the Brown Skin: Atlas and Short Text. Khopkar US (Ed). New Delhi: Jaypee Brothers Medical Publishers (P) Ltd; 2012. pp. 10–37.
- Kaliyadan F. The scope of the dermoscope. Indian Dermatol Online J. 2016;7:359–63.
- Micali G, Verzì AE, Lacarrubba F. Alternative uses of dermoscopy in daily clinical practice: an update. J Am Acad Dermatol. 2018;79:1117–32.
- Sonthalia S, Yumeen S, Kaliyadan F. Dermoscopy Overview and Extradiagnostic Applications. In: StatPearls [Internet]. Treasure Island (FL): Stat Pearls Publishing; 2021.
- Sonthalia S, Pasquali P, Agrawal M, Sharma P, Jha AK, Errichetti E, et al. Dermoscopy update: review of its extradiagnostic and expanding indications and future prospects. Dermatol Pract Concept. 2019;9:253–64.
- Marghoob AA, Usatine RP, Jaimes N. Dermoscopy for the family physician. Am Fam Physician. 2013;88:441–50.
- Zalaudek I, Kreusch J, Giacomel J, Ferrara G, Catricalà C, Argenziano G. How to diagnose nonpigmented skin tumors: a review of vascular structures seen with dermoscopy: Part I. Melanocytic skin tumors. J Am Acad Dermatol. 2010;63:361–74.
- Zalaudek I, Kreusch J, Giacomel J, Ferrara G, Catricala C, Argenziano G. How to diagnose nonpigmented skin tumors: Part II. Non-melanocytic skin tumors. J Am Acad Dermatol. 2010;63:377–86.
- Venugopal SS, Soyer HP, Menzies SW. Results of a nationwide dermoscopy survey investigating the prevalence, advantages and disadvantages of dermoscopy use among Australian dermatologists. Australian J Dermatol. 2011;52:14–8.
- Chappuis P, Duru G, Marchal O, Girier P, Dalle S, Thomas L. Dermoscopy, a useful tool for general practitioners in melanoma screening: a nationwide survey. Br J Dermatol. 2016;175:744–50.
- Shen XW, Yu RX, Shen CB, Li CX, Jing Y, Zheng YJ, et al. Dermoscopy in China—current status and future prospective. Chin Med J. 2019;132:2096–104.
- Skvara H, Teban L, Fiebiger M, Binder M. Limitation of dermoscopy in the recognition of melanoma. Arch Dermatol. 2005;14:155–60.
- Uppal SK, Beer J, Hadeler E, Gitlow H, Nouri K. The clinical utility of teledermoscopy in the era of telemedicine. Dermatol Ther. 2021;34:e14766.