Enlarged rete pegs with excessive accumulation of melanosomes leading to darker aging spots revealed by histomorphological measurements of internal structures of the epidermis.

From the measurements of quantitative parameters, morphological changes in the epidermis were clearly related to the surface color tone of pigmented spots. Darker pigmented spot sites tended to show longer rete pegs in the epidermis. Accumulation of melanosomes in epidermal basal cells could be considered to increase with the degree of elongation of rete pegs at pigmented spot sites and thus induce darker pigmented spots.