A Becker's nevus appears around puberty as a unilateral brown patch that develops coarse hairs, a different color, onset, and features.
A café-au-lait macule is light brown, not bluish-grey like a Mongolian spot.
A CMN is a brown-to-black mole, which is a proliferation of melanocytes, whereas a Mongolian spot is due to dermal melanocytosis and typically fades.
