(a) In situ melanoma arising within a congenital lesion, 4 mm, abdomen, 34-year-old male. Peripheral pink with some eccentric pink centrally: in situ melanoma, 4 mm wide, right abdomen, arising within a superficial compound congenital nevus; pink rim sign is present (arrows) just external to irregular network lacking pink. Note negative network and peripheral globules that are fairly uniform and symmetric. (b) Pink throughout lesion: benign nevus, not biopsied, 5 mm nevus on upper arm in 35-year-old female; pink is present at rim but is most prominent centrally (arrows). Pink rim sign is absent. Note similar architecture and symmetrically arranged globules in both lesions.