Formalin-fixed tissue samples were stained with H&E for histological description. Masson-Fontana (MF) staining was performed for characterization of the pigmentation pattern. Immunohistochemical procedures were performed on 20 representative SL derived in equal parts from the hand and the face. Tissue samples were fixed in 4% formaldehyde overnight and embedded in paraffin. Paraffin-embedded blocks were sectioned at a 6-μm thickness and deparaffinized in xylene, hydrated with ethanol, and rinsed in distilled water. Citrate buffer incubation (40 min, 10 mM citric acid, 0.05% Tween 20, pH 6) in a steamer was used for epitope retrieval. Afterwards, sections were cooled for 20 min and rinsed in phosphate-buffered saline. The following primary antibodies were used: anti-melan A (1: 60; Leica Microsystems), anti-tyrosinase (1: 60; Novocastra), anti-MITF (clone D5, 1: 60; Dako) p53 (1: 60; Dako), and anti-CD20 (1: 60; Dako). Notch1 immunofluorescence staining (Cell Signaling Technology) was performed on 12 of those lesions (5 lesions derived from the face and 7 lesions from the hand), according to a previously described method [14 (link)]. All tissue samples were microscopically observed in ×40 magnification (Olympus BX51TF).