Acral Speckled Lentiginous Nevus

Speckled lentiginous nevus (SLN), also referred to as nevus spilus, is a common benign melanocytic neoplasm typically occurring as a small, café-au-lait-colored "speckled" patch studded with numerous darkly pigmented macules or papules. Herein, we present a unique case of SLN arising on the sole of the right foot in a young woman, which was reported to be gradually enlarging since a pregnancy two years prior. The lesion was removed by shave biopsy, and histopathology confirmed the diagnosis and ruled out atypical features. While SLN is quite common, the occurrence on acral skin is extremely rare. SLN is considered a mosaic RASopathy due to its embryological development through a postzygotic activating HRAS genetic variant. Although small lesions usually remain isolated, underlying SLN syndrome should be considered in extensive cases with associated neurologic or musculoskeletal abnormalities. Secondary melanocytic neoplasms commonly arise within SLN, but overall, small lesions carry a low risk of malignant transformation, and prophylactic surgical treatment is not necessary. We briefly discuss SLN occurring in special sites and report this novel case with a review of the literature on SLN.