Emi Dika, Marco Adriano Chessa, Simone Ribero, Pier A. Fanti, Carlotta Gurioli, Martina Lambertini, Carlotta Baraldi, Annalisa Patrizi
DOI: 10.2340/00015555-2705

The introduction of dermoscopy has improved the accuracy of diagnosis of melanoma. However, early stage melanoma can be difficult to diagnose. Eighty-nine cases of thin melanoma with a Breslow thickness ≤1 mm located on the lower limb and diagnosed between 2008 and 2016 were assessed using 4 dermoscopic algorithms: (i) modified pattern analysis; (ii) ABCD rule of dermoscopy; (iii) 7-point checklist; and (iv) Menzies’ method. Two groups of early stage melanomas of the legs were identified: “difficult to diagnose melanomas” (DDM) and “non-difficult to diagnose melanomas” (NDDM). In our series the dermoscopic features of DDM were difficult to differentiate from melanocytic naevi, and the reticular pattern was the most frequently observed. “Depigmentation” was the only specific criterion associated with DDM. The sensitivity of diagnostic systems for thin melanomas of the lower limbs was lower than in previous studies. This result could be related to the lower mean Breslow thickness of the invasive melanomas in our sample and the high number of melanomas in situ. In conclusion, early stage melanoma of the legs may be difficult to detect at clinical examination or with dermoscopic examination alone. Focusing on depigmentation in dermoscopy associated with anamnestic features could be a useful tool to detect difficult thin melanomas. In addition, sequential dermoscopy is recommended for high-risk patients with previous melanomas or atypical mole syndrome.