Small diameter melanocytic lesions: morphological analysis by means of in vivo confocal microscopy

BACKGROUND: small diameter melanocytic lesions represent a diagnostic challenge for clinicians since they do not follow the ABCD rule and do not always display reliable histopathologic criteria OBJECTIVES: The aim of the study was to analyze the confocal features of small diameter lesions (naevi and melanomas with diameter ≤ 5 mm) to determine whether they show specific morphologic criteria PATIENTS AND METHODS: 24 melanomas and 72 naevi were subjected to dermoscopic and confocal evaluation along with histopathology. Significant dermoscopic and confocal differences between melanomas and naevi were evaluated by means of Pearson's Chi-square. Odds ratios and 95% confidence interval were calculated for each parameter. Binary logistic regression was calculated to identify the RCM independently significant features for melanoma diagnosis. RESULTS: The 7-point checklist dermoscopic score was ≥ 3 in 22 melanomas and in 33 naevi. The combination of cells' pleomorphism and architectural disorder (i.e. non specific pattern or irregular junctional nests upon confocal examination) are the most striking criteria for consistent small melanoma diagnosis. Presence of atypical cells, >5 atypical cells per mm(2) and roundish atypical cells at DEJ showed the highest odds ratios values. From logistic regression presence of > 5 pagetoid cells per mm(2) , tangled lines within the epidermis, atypical roundish cells at DEJ resulted to be the three independent confocal parameters that characterized small melanomas. CONCLUSIONS: small melanomas frequently reveal specific dermoscopic and confocal features. Moreover the combination of dermoscopy and RCM can lead to a correct diagnosis of a quote of naevi that share some morphologic aspects with melanomas.