Dermoscopy of small melanomas: just miniaturized dermoscopy?

Background Small malignant melanomas (MMs) are usually MMs in an initial growth phase, deserving attention by the clinician aiming at an early diagnosis. Objectives To identify clues for early diagnosis of small MMs, by comparing the dermoscopic features of MMs < 4 mm (micromelanomas) with those of larger MMs. Methods Our database consists of dermoscopic images of 482 MMs, which have been retrieved and measured digitally. The ABCD (asymmetry, border, colour, dimension) and 7-point criteria were evaluated for the whole database by three expert dermoscopists, whereas the main dermoscopic pattern was assessed only for micromelanomas. The dermoscopic aspects were correlated to clinical and histological features. Results Most 7-point and ABCD scores, and criteria referring to micromelanomas, differed from those of the MM database as a whole. Lesion asymmetry, number of colours, blue-whitish veil, atypical vessels, irregular globules/dots and regression increased according to MM diameter. An inverse trend was observed for atypical network and irregular pigmentation, which were more frequently observed in micromelanomas than in larger ones. Among the 22 micromelanomas, 12 lesions were in situ, whereas the other 10 were 0.2-2 mm thick. The clinical and dermoscopic characteristics of the two groups were similar. Conclusions Micromelanomas are not a rarity. However, the clinician should be aware of the fact that the majority of them lack most of the dermoscopic features presented by larger lesions.