Dermatologists use patterns to recognize melanoma

Apr 19 2005

Dermatologists depend on overall pattern recognition and comparison rather than specific analytic criteria to distinguish melanoma lesions (malignant skin cancer) from harmless skin moles, according to an article in the April issue of Archives of Dermatology.

Early detection is the key to reducing the death rate from melanoma, but most people, including general practitioners, are not able to distinguish melanoma from harmless moles, according to background information in the article. Helping people to detect their own melanoma in the past has relied on analytic formulas like the ABCD rule, which teaches looking for A, asymmetry; B, irregular borders; C, uneven color; and D, diameter. The authors suggest that assessing how dermatologists spot melanoma may offer better ways of teaching the general public what to look for and to use to develop a training model for general practitioners.

Julie Gachon, M.D., of the Hôpital Ste. Marguerite, Marseille, France, and colleagues assessed dermatologists' recorded immediate perceptions as well as their intuitive diagnosis of 4,036 either harmless or malignant moles (lesions) that they had decided to remove for any reason and compared that information with the final diagnosis of the lesion based on a laboratory analysis. One hundred-thirty-five dermatologists, most of whom were community physicians in private practice, recorded their overall impression of the lesion, based on their past experience; assessed the lesion using the analytic ABC criteria; recorded their impression of how different the lesion was from the patient's other skin moles (the ugly duckling sign); and noted how the lesion had changed, according to the patient. The physicians completed a second part of the questionnaire after they obtained the pathology report.

Of the 4,036 lesions removed, 1,634 were removed (40.7 percent) for aesthetic or functional reasons, 535 (13.3 percent) "only to reassure the patient", 1,199 (29.7 percent) because the dermatologist considered them suspicious and 869 (21.5 percent) because the dermatologist thought they might be precursors to melanoma. These different reasons accounted for two (1.3 percent), nine (6.0 percent), 141 (94.6 percent) and 14 (9.4 percent) of the 149 lesions that were determined to be melanoma.

"Among the different perceptions of a lesion by a dermatologist, those most relevant to making an accurate diagnosis of MM [melanoma] seem to be the feeling that this lesion is overall irregular by reference to the usual nevi [moles and beauty marks], the perception of an ugly duckling sign by reference to the other nevi in the subject, and, to a lesser degree, the knowledge that the lesion has recently changed," the authors write.

"The overall recognition process, mimicking experts in their daily practice, could be useful in the field of education at MM detection," the authors state. "Indeed a learning process with photographs, based on a global cognitive approach, is worth being assessed. .Our study also confirms how much a recent change is important for a reliable diagnosis of MM. In this regard, the fact that an MM was found in nine (1.68 percent) of the 535 nevi that were removed only to reassure the patient should lead physicians to listen carefully to patients who want a mole resected [removed], because patients may perceive subtle changes that they may be unable to communicate."