Dermoscopy demands skill, systematic approach

December 1, 2005

Chicago — The use of dermoscopy can improve dermatologists' accuracy in diagnosing pigmented lesions, but only if it is done properly.

Chicago - The use of dermoscopy can improve dermatologists' accuracy in diagnosing pigmented lesions, but only if it is done properly.

Unlike textbook examples, "There are innumerable variations of all the classic diagnostic criteria and patterns. That's why it is very important to know the basics," Robert Johr, M.D. says. "If one doesn't see a classic dermoscopic picture, it is essential to be knowledgeable enough to create a dermoscopic differential diagnosis and think things through just as one would do in other clinical situations. That's one of the major problems with physicians I've seen - they think they can use dermoscopy without learning the basics. Studies have shown that with this approach, diagnostic accuracy decreases."

Dr. Johr is clinical professor of dermatology and pediatrics (and director of the Pigmented Lesion Clinic) at the University of Miami, and a Boca Raton, Fla.-based private practitioner.

To accurately diagnose a pigmented lesion, dermatologists must first determine whether it's melanocytic or non-melanocytic. Hallmarks of melanocytic lesions include pigment network, dots and globules, homogeneous blue color and parallel patterns on acral sites.

If a lesion fails to meet the criteria for a melanocytic lesion or seborrheic keratosis, one must then consider whether or not it could be a basal cell carcinoma (BCC). Dr. Johr says that the most important criteria are in-focus, arborizing or thickened, branched blood vessels. They look like bright red lines that are in focus because they're superficially located in the lesion.

If the lesion does not appear to be a BCC, it may be a dermatofibroma or a vascular lesion. A dermatofibroma is characterized by a bony white patch and thin pigment network; vascular lesions possess variously sized, in-focus vascular spaces called lacunae. If all of the primary criteria are not identified, Dr. Johr explains, "one should consider it to be a melanocytic lesion by default. The next step is to determine if it's benign or malignant. There is, however, a large gray zone of equivocal lesions that take some extra time and thought to come up with a dermoscopic diagnosis."

Dr. Johr adds, that even if a lesion has several melanoma-specific criteria, one never should tell a patient it's certain that he or she has a melanoma. Dermoscopy is not a 100 percent diagnostic technique, and even the worst clinical and dermoscopic appearances can turn out to be benign. That would be the time to seek other histopathologic opinions.

Melanoma

Melanoma-specific criteria include various warning signs: