Acral-lentiginous naevus of plantar skin

In a consecutive series of 165 plantar naevi, a group of 36 benign naevi with sufficiently distinctive histopathological features to justify their classification as a special entity, here designated acral-lentiginous naevus, was identified. The main morphological features distinguishing the acral-lentiginous naevi from other acral non-lentiginous naevi are: elongation of rete ridges, continuous proliferation of melanocytes at the dermo-epidermal junction, presence of single scattered melanocytes, or less commonly small clusters, within the upper epidermis, poor or absent lateral circumscription, melanocytes with abundant pale cytoplasm and round to oval, sometimes hyperchromatic, nuclei and prominent nucleoli present at the dermo-epidermal junction. Some histological features of acral-lentiginous naevi are similar to those of dysplastic naevi: however, anastomosing rete ridges, cytological atypia and well-formed lamellar fibroplasia are absent. The histopathological criteria to distinguish these naevi from melanoma are: the lack of pagetoid lateral spread, the absence of mitotic activity in the deep dermal component and the evidence of dermal naevocytic differentiation. The identification of this benign acral naevus, that we have identified as the benign counterpart of acral lentiginous melanoma, is important in order to avoid misdiagnoses and consequent under- or over-treatment of doubtful pigmented lesions of acral skin.