Dermoscopic spectrum of mycosis fungoides: a retrospective observational study by the International Dermoscopy Society.

BACKGROUND: The dermoscopic features of classic patch stage mycosis fungoides (MF) have been described, but data on plaque and tumoral stage as well as rarer MF subtypes is limited. OBJECTIVE: To evaluate dermoscopic morphology and dermoscopic-pathological correlations of classic MF stages and investigate dermoscopic features of MF variants. METHODS: Patients with histopathologically confirmed lesions of classic MF (patch, plaque and tumoral stage) or folliculotropic, erythrodermic and poikilodermatous MF were included. Standardized evaluation of dermoscopic pictures of the included MF variants and comparative analysis and dermoscopic-pathological correlation assessment of different stages of classic MF were performed. RESULTS: A total of 118 instances were included (75 classic MF, 26 folliculotropic MF, 9 erythrodermic MF and 8 poikilodermatous MF). Linear/linear-curved vessels and white scales in the skin furrows were significantly associated with patch-stage MF, while clustered dotted vessels were related to plaque-stage MF and peripheral linear vessels with branches, ulceration and red globules separated by white lines to tumour-stage MF. Moreover, patchy white scales were significantly more common in patches and plaques compared to tumours, whereas focal bright white structureless areas were related to plaque and tumoral stage. Vessels histopathologically corresponded to dilated vascular structures in the dermis, orange structureless areas to either dermal hemosiderin (patch/plaque stage) or dense cellular infiltration (tumours), bright white lines/structureless areas to dermal fibrosis and ulceration to loss of epidermis. The main dermoscopic findings of folliculotropic MF were lack of hairs, dilated follicles and follicular plugs, while erythrodermic MF was mainly characterized by linear/dotted vessels, patchy white scales and focal orange structureless areas and poikilodermatous MF by focal white and brown structureless areas, white patchy scales and brown reticular lines. CONCLUSION: Dermoscopy may allow a more precise characterization of classic MF and reveal clues suggestive of the main MF variants.

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.