Dermatology World August 2011 : Page 33
parietal regions. A hair diameter diversity of greater than 20 percent is highly speci c of the disease. Although the use of dermoscopy to diagnose psoriasis is still developing, investigators using the higher magni cations of video dermoscopy have identi ed dilated, elongated, and convoluted capillaries in a distinctive “bushy” pattern that is peculiar to psoriasis. “This is important because some forms of psoriasis are very limited, and the physician can’t make a diagnosis without a biopsy and patch test if contact dermatitis is suspected,” Dr. Micali said. “If you use dermoscopy and you nd this vascular pattern, then the diagnosis is simple. We tested this with a group of patients who had a single patch on the hand. In those patients who did not show this bushy pattern, histology con rmed a diagnosis of spongy dermatitis. All patients with the bushy pattern were found to have psoriasis.” For psoriasis patients on biologic therapy, dermoscopy can help to rule out a return of the disease, Dr. Micali said. “Sometimes they might also have nonspeci c skin in ammation, or eczema, and think it’s psoriasis. Dermoscopy can tell us if it is or is not.” DETECTING MELANOMA AND NON MELANOMA SKIN CANCER Dermoscopy initially gained recognition as an e ective method for the early recognition of malignant melanoma during the 1990s. According to a clinical review article published in JAAD (2005;52:109-21) dermoscopy “increases diagnostic accuracy between 5 percent and 30 percent over clinical visual inspection, depending on the type of skin lesion and experience of the physician.” Technological advances in the past ve years have yielded improvements in convenience and clinical utility, noted Ashfaq A. Marghoob, M.D., the editor of the Atlas of Dermoscopy , a guide to the early recognition of melanoma. “The discovery that polarized light can be used to see dermoscopic structures without the need to touch or wet the skin was particularly important,” said Dr. Marghoob, an associate clinical professor of dermatology at Memorial Sloan-Kettering Cancer Center and the State University of New York at Stony Brook. “There’s certainly a convenience factor, but what we found was that there are structures you can see under polarized light that you can’t see under non-polarized light, and vice versa. The two modes are complementary, and there may be features only distinguishable with one type that are critical for the diagnosis of a particular lesion. So most experts now are leaning toward the use of hybrid scopes that allow you to toggle between polarized and non-polarized light when evaluating a lesion.” Dermoscopy has clearly improved the sensitivity of the diagnosis of melanoma, Dr. Marghoob said. “It has especially improved our ability to detect the hypomelanotic and amelanotic melanomas, because there are dermoscopic criteria for non-pigmented lesions. These lesions would be visible to the naked eye but would not meet the ABCD criteria; they may be smaller than 6mm, for example. Dermoscopy would help you diagnose them.” Similarly, dermoscopy has improved the early diagnosis of non-melanoma skin cancers. “It has given us the ability to detect basal cell carcinomas and squamous cell carcinomas even when they’re as tiny as 1mm,” Dr. Marghoob said. “The advantage, obviously, is that whatever scar you’re going to end up with will be smaller.” Sequential digital dermoscopy, the short-term monitoring of nevi for which a diagnosis is unclear, can also lead to the very early detection of melanomas. “Sometimes we see melanomas in which there are no criteria to make a diagnosis, so we take a dermoscopic image and then take another three months later. If any change occurs, it gets removed,” Dr. Marghoob said. “We’ve gotten to the point where we’re diagnosing clinically featureless melanomas. They’re also featureless on dermoscopy, but based on the change seen dermoscopically, they’re being diagnosed.” Improving the benign to malignant ratio of biopsied pigmented lesions and reducing the number of unnecessary excisions through dermoscopy is a key bene t to patients, said the experts. But leaving a lesion in place requires recognition of the dermoscopic features of benign lesions, as well as melanomas. Kelly Nelson, M.D., director of the melanocytic lesions clinic and assistant professor of dermatology at Duke University Medical Center, sought to address an issue that was a ecting her pediatric patients. “I had several patients with very large scars on their scalp because their doctors had noted moles and excised them. In some young patients it was almost deforming; they looked as though they had been in a car accident,” she said. “There was little information about typical nevi in children, so we decided to conduct a study to establish the clinical and dermoscopic patterns of typical scalp nevi in patients younger than 18.” Dr. Nelson and her colleagues obtained clinical and dermoscopic images of 88 nevi in 39 children referred to either the pediatric dermatology clinic or the pigmented lesion clinic for other reasons. Based on the reassuring dermoscopic patterns observed, none of the nevi were excised. The study, which discusses in detail the clinical and dermoscopic features of the nevi, will be published in DERMATOLOGY WORLD // August 2011 33
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