Dermatoscopy of combined blue nevi: a multicentre study of the International Dermoscopy Society.

BACKGROUND: Combined blue nevi (CBN) may mimic melanoma and are relatively often biopsied for diagnostic reasons. OBJECTIVE: To better characterize CBN and to compare it with melanoma. METHODS: We collected clinical and dermatoscopic images of 111 histologically confirmed CBN and contrasted their dermatoscopic characteristics with 132 partly blue coloured melanomas. Furthermore, we compared the accuracy of human experts using pattern analysis with a computer algorithm based on deep learning. RESULTS: Combined blue nevi are usually flat or slightly elevated and, in comparison with melanoma, more frequent on the head and neck. Dermatoscopically, they are typified by a blue structureless part in combination with either brown clods (n = 52, 46.8%), lines (n = 28, 25.2%) or skin-coloured or brown structureless areas (n = 31, 27.9%). In contrast with melanoma, the blue part of CBN is more often well defined (18.9% vs. 4.5%, P < 0.001) and more often located in the centre (22.5% vs. 5.3%, P < 0.001). Melanomas are more often chaotic (OR: 28.7, 95% CI: 14.8-55.7, P < 0.001), have at least one melanoma clue (OR: 10.8, 95% CI: 5.2-22.2 P < 0.001) in particular white lines (OR: 37.1, 95% CI: 13.4-102.9, P < 0.001). Using simplified pattern analysis (chaos and clues), two raters reached sensitivities of 93.9% (95% CI: 88.4-97.3%) and 92.4% (95% CI: 86.5-96.3%) at corresponding specificities of 59.5% (95% CI: 49.7-68.7%) and 65.8% (95% CI: 56.2-74.5%). The human accuracy with pattern analysis was on par with a state-of-the-art computer algorithm based on deep learning that achieved an area under the curve of (0.92, 95% CI: 0.87-0.96) and a specificity of 85.3% (95% CI: 76.5-91.7%) at a given sensitivity of 83.6% (95% CI: 72.5-91.5%). CONCLUSION: CBN usually lack melanoma clues, in particular white lines. The accuracy of pattern analysis for combined nevi is acceptable, and histopathologic confirmation may not be necessary in exemplary cases.

Changes in common melanocytic naevi after intense sun exposure: digital dermoscopic study with a 1-year follow-up.

BACKGROUND: Exposure to ultraviolet (UV) radiation induces acute changes in common melanocytic naevi (CMN). AIM: To analyse changes in size and dermoscopic structures of CMN in healthy individuals under the influence of intense sun exposure and to investigate effectiveness of sunscreen usage in preventing the appearance of dermoscopic changes. METHODS: The subjects were divided into an SS group and a non-SS group, according to whether they used sunscreen or not. Digital epiluminiscence microscopy (DELM) was performed before sun exposure and 28 days and 1 year after the cessation of intense sun exposure. RESULTS: Eleven subjects with 60 naevi fulfilled the inclusion criteria. A significant increase in one diameter of the CMN was found 28 days after cessation of sun exposure, irrespective of sunscreen usage. There was no significant change in total dermoscopy score during the follow-up period in either the SS or non-SS group. There were definitive DELM changes at the 1-year follow-up in 10% of CMNs < 5 mm in size. Changes in pigmented network, globules and streaks were fully reversible in the remaining CMN. The use of sunscreen had no influence on these changes. CONCLUSIONS: The increases in the size of melanocytic naevi that we found 28 days after cessation of intense sun exposure are probably induced by UV radiation, whereas changes in DELM features that were not reversible in some small naevi at the 1-year follow-up could be related both to sun exposure and to the natural evolution of the naevi. The use of sunscreen does not seem to prevent these changes. Small naevi in low-risk young and middle-aged patients seem to be more prone to sun-induced DELM changes.

Generalized acanthosis nigricans in early childhood.

Acanthosis nigricans (AN) is a disorder often accompanied by internal malignancy in adult patients, but in children it is usually benign. Generalized forms of AN, especially in childhood, are extremely rare. We report a 5-year-old boy with a 3-year history of AN who had generalized roughness and hyperpigmentation, numerous skin wrinkles, disseminated skin tags, tripe palms, and intensive pruritus. No clinical evidence of internal disorders, notably of an endocrinologic or neoplastic nature, have been detected thus far.