'Ugly Duckling' Moles May Be Melanomas

By Judith Groch
NEW YORK, Jan. 21 -- An irregularly pigmented mole that looks different from other irregularly pigmented moles in the same person -- an "ugly duckling" -- is likely to be a malignant melanoma, according to a preliminary study. In a small study, all five melanomas and only three of 140 benign lesions (2.1%) were identified as ugly ducklings by two-thirds of hospital-staff participants with varying expertise, reported Ashfaq Marghoob, M.D., of Memorial Sloan-Kettering Cancer Center here, and colleagues in the January issue of the Archives of Dermatology.
Nevi are among the most important known risk factors for malignant melanoma in adults, and the skin cancer is more common in individuals with many nevi, including dysplastic ones, Dr. Marghoob's team wrote.
The challenge for clinicians who diagnose and treat pigmented skin lesions is to distinguish between melanoma and similar-looking benign lesions. There is an overlap in the moles' clinical features that leads to missed melanomas and excessive excision of benign lesions, the researchers said.
In 1998, investigators introduced the ugly duckling concept to demonstrate that nevi in the same individual tend to resemble one another and that those that deviate from the pattern tend to be melanomas.
To determine whether the ugly duckling sign is sensitive for melanoma detection, the researchers had 34 staff members of a dermatology clinic examine baseline back images of 12 patients.
The images, supplemented with close-up clinical images, were obtained from a database of standardized patient images. All 12 patients had at least eight atypical moles on the back, and in five patients, one of the lesions was a histologically confirmed melanoma.
The 34 observers included eight pigmented-lesion specialists, 13 general dermatologists, five dermatology nurses, and eight members of the nonclinical staff.
Participants were asked to evaluate whether the images showed any lesions on the back that differed from other nevi.
A lesion was considered a generally apparent ugly duckling if it was perceived as different by at least two-thirds of the participants.
Sensitivity was defined as the fraction of melanomas identified as different. Specificity was defined as the number of nevi not identified as different divided by the total number evaluated.
All five melanomas (100%) and only three of 140 benign lesions (two nevi and one seborrheic keratosis) were generally apparent as different, meaning that they were ugly ducklings.
The agreement on ugly ducklings decreased among participants in the groups with less expertise. The sensitivity of the ugly duckling sign for melanoma detection was 90% for the whole group, 100% for specialized dermatologists, 89% for general dermatologists, 88% for nurses, and 85% for nonclinicians.
The melanomas were apparent as being different to at least 85% of participants, whereas the agreement rate on the benign lesions perceived as being different was 76% at most, the researchers said.
Four lesions were generally apparent as completely different, all being melanomas. The single melanoma that was not generally apparent as completely different was an irregular brown macule, one centimeter in diameter, with a central black area. Nevertheless, the pigmented-lesion specialists made a correct identification.
Still, the values for all parameters were good in all subgroups of participants, the researchers said. Identification of ugly ducklings showed good sensitivity (0.87) and specificity (0.83) and diagnostic accuracy (0.87) for the detection of melanoma, even among nonclinicians.
Interestingly, the researchers noted, pigmented seborrheic keratosis and melanoma can resemble each other, and the seborrheic keratoses are unlikely to appear similar to a patient's prevalent nevus pattern. Thus, these lesions may be the Achilles' heel of the ugly duckling strategy, they said.
A limitation of the study, the investigators noted, is that assessment was done in a virtual setting rather than a real-time examination.
Also, dermoscopy was not used, possibly affecting diagnosis for those who use the method frequently in clinical practice.
Furthermore, they said, sensitivity and specificity values were primarily used as a means of measuring quantitative differences among expertise levels, and these values may not reflect actual values in the real world.
Finally, they said, the term "different" -- size, color, shape, or a combination -- was not defined precisely.
These preliminary findings, the researchers wrote, should be further assessed to allow refinement of the ugly duckling sign. However, they said, the sign may prove a useful screening strategy for primary health care providers and even for self-examination.
No financial conflicts were reported.
Primary source: Archives of DermatologySource reference:Scope A, et al "The 'ugly duckling' sign: agreement between observers" Arch Dermatol 2008; 144: 58-64.