An increasing number of thin (< or = 1 mm) cutaneous malignant melanomas are currently diagnosed. The majority of thin lesions is associated with an excellent prognosis, however, some of them may develop local recurrences and/or distant metastases with fatal outcome. Although Breslow thickness is the single most significant prognostic factor in melanoma in general, for thin lesions the identification of other morphological, biological and/or molecular parameters which may have an impact on neoplastic progression is mandatory. At present, Clark's levels and ulceration are regarded as significant prognostic factors. Further studies are needed to confirm the prognostic value of other histopathological parameters, including the evaluation of regression, inflammatory infiltrate and mitotic activity.