Dermoscopy: An Invaluable Tool for Evaluating Skin Lesions
Am Fam Physician. 2008 Sep 15;78(6):704-706.
Dermatoscopes are instruments that employ light and magnification to evaluate skin lesions. The most common types are shaped much like otoscopes; one type of dermatoscope is depicted in the article by Dr. Cyr in this issue of American Family Physician.1 Most dermatoscopes are applied directly against the skin. These use a fluid interface to make the skin surface more transparent, allowing visualization not only of the surface of skin lesions, but also of subsurface structures, aiding in lesion identification. For a trained dermoscopist, the diagnosis for a clinically indeterminate, but dermoscopically characteristic lesion can often be ascertained within one to two seconds. With experience, it should be very rare that a lesion requires more than 10 seconds to evaluate. As pointed out by Dr. Cyr, a particular strength of dermoscopy is assessing which lesions are melanocytic, and for those that are, which are the most worrisome and worthy of biopsy to avoid missing the diagnosis of melanoma.
Studies indicate that primary care physicians are less adept at identifying melanomas than dermatologists.2 However, one study demonstrated that primary care physicians can, with one day of training, meaningfully improve their in-practice clinical diagnostic accuracy for cutaneous melanoma using dermoscopy compared with naked eye examination, improving their sensitivity (79 versus 54 percent, respectively) without reducing specificity (71.5 percent).3 Dermatoscopes (with a rechargeable handle) are available for about $500 and up.4
As someone whose clinical practice relies on dermoscopy, the most common question I am asked related to dermoscopy is, “What is the reimbursement for this procedure?” The answer is the satisfaction of finding early melanomas (saving lives) and improving diagnostic accuracy while saving time. As an extension of the physical examination, just like otoscopy or stethoscopy, there is no extra reimbursement. However, I can no more envision evaluating skin without a dermatoscope than I can a tympanic membrane without an otoscope or a heart without a stethoscope. I have “blown by” lesions on routine examination only to apply the dermatoscope and identify suspected melanomas. I am indebted to dermoscopy for making decisions easier and quicker every day.
To effectively evaluate skin, excellent light and magnification are needed.5,6 The visual portion of diagnosis is based on distribution and morphology.5,6 For neoplasms, the major clinical decision is whether a lesion is safe to stay or if it should be removed.7 Dermatoscopes have critical value because they provide light and magnification; illuminate morphology not otherwise visible (subsurface lesion structure); and assist in determining whether a lesion has sufficient comfort features to deem it safe to stay.
In the examination room, I introduce the dermatoscope to new patients as a “skin microscope.” I indicate that it is a bright light and a magnifying glass, and that ultrasound gel (water soluble, nontoxic) is used with it to make the skin more translucent, allowing assessment of the lesion's subsurface structure. The original intent of dermoscopy was to evaluate melanocytic lesions, specifically for earlier diagnosis of melanoma because in situ and thin melanomas have a good prognosis. However, dermoscopy has grown well beyond evaluation of melanocytic lesions.
Certainly for many rashes, dermoscopy is of little value. However, there may be just one plaque of psoriasis to help with diagnosis, and the patient could present partially treated at the time of evaluation. Dermoscopy can assist in evaluating vascular patterns to suggest the correct diagnosis. A solitary papulosquamous plaque could also represent squamous cell carcinoma in situ, especially if dermoscopy reveals glomerular vessels. Similarly, dermoscopy may show telangiectatic vessels in basal cell carcinoma that were undetected with the naked eye, which would help determine the correct diagnosis. Although not usually scaly, amelanotic or hypomelanotic melanoma and Spitzoid lesions can present as pink papules or plaques. Basal cell carcinoma can be shaved for diagnosis; however, shave biopsy on melanoma should be avoided1 because you lose the ability to determine Clark level and Breslow depth. Prebiopsy distinction is important, and this is another area where dermoscopy is invaluable. For example, dermoscopy can instantly transform a papule of uncertain etiology to molluscum, or show a dermoscopic pattern that is virtually diagnostic of scabies.
Dermoscopy is also useful in differentiating seborrheic keratoses from melanocytic lesions, which is a common clinical dilemma. For dermoscopic evaluation of melanocytic lesions, the three-point checklist (assessing the lesion's network pattern, color, and structural symmetry) is the simplest evaluation tool. Melanocytic lesions that “fail” should generally be excised to rule out melanoma.7
Dermoscopy is only one piece of the entire clinical picture. “Ugly ducklings” (lesions that are distinctly different from everything else in their neighborhood) should always be immediately scrutinized.8 Dermoscopy should never be entirely reassuring when lesion history is worrisome.9 Even for melanoma, pathologic interpretation is an art.10,11 Thus, physicians should send all skin biopsies to dermatopathologists, discuss clinicopathologic disconnects with the dermatopathologist, and request second opinions when necessary.
For those contemplating dermoscopy, I would recommend:
Reading an introductory textbook, Dermoscopy: The Essentials.7
Reading the comprehensive textbook, Atlas of Dermoscopy, because it details melanoma-specific criteria, and systematizes analysis of pigmented and nonpigmented lesions.12
Joining the online International Society of Dermoscopy discussion forum (http://www.dermoscopy-ids.org/discussion/ [registration required]), and reviewing the new postings as continuing dermoscopic education. My suggestion would be to review the dermoscopic images, form your own opinion, and then read the experts' postings and histologic correlation. The persons engaging in discussion on this list are world experts who are advancing the frontiers of dermoscopy.
Like a scalpel, the dermatoscope is an awesome instrument in trained hands. As with wielding a scalpel, one should not engage in dermoscopy without some basic training. Finally, for those who devote the time to become proficient dermoscopists, my suggestion (having used both a 10X and 20X dermatoscope) would be to invest in a 20X dermatoscope.
1. Cyr PR. Atypical moles. Am Fam Physician. . 2008;78(6):735–740.
2. Chen SC, Pennie ML, Kolm P, et al. Diagnosing and managing cutaneous pigmented lesions: primary care physicians versus dermatologists. J Gen Intern Med. 2006;21(7):678–682.
3. Argenziano G, Puig S, Zalaudek I, et al. Dermoscopy improves accuracy of primary care physicians to triage lesions suggestive of skin cancer. J Clin Oncol. 2006;24(12):1877–1882.
4. Miami Medical. Episcope. http://www.miami-med.com/episcope.htm. Accessed March 26, 2008.
5. Habif, TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 4th ed. New York, NY: Mosby; 2004.
6. Roenigk HH. Office Dermatology. Baltimore, Md.: Williams & Wilkins; 1981.
7. Johr R. Dermoscopy: The Essentials. New York, NY: Mosby; 2004.
8. Grob JJ, Bonerandi JJ. The ‘ugly duckling’ sign: identification of the common characteristics of nevi in an individual as a basis for melanoma screening. Arch Dermatol. 1998;134(1):103–104.
9. Braun RP, Gaide O, Skaria AM, Kopf AW, Saurat JH, Marghoob AA. Exclusively benign dermoscopic pattern in a patient with acral melanoma. Arch Dermatol. 2007;143(9):1213–1215.
10. McBroom HM, Ramsay AD. The clinicopathological meeting. A means of auditing diagnostic performance. Am J Surg Pathol. 1993;17(1):75–80.
11. Farmer ER, Gonin R, Hanna MP. Discordance in the histopathologic diagnosis of melanoma and melanocytic nevi between expert pathologists. Hum Pathol. 1996;27(6):528–531.
12. Marghoob AA, Braun RP, Kopf AW. Atlas of Dermoscopy. New York, NY: Taylor & Francis; 2005.
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