system
Given the following post, respond as if you're commenting on Reddit:
human
If skin cells are one of the fastest replicating cells, how come moles, and birth marks don’t disappear over time?

Same goes for warts and scars.
gpt
Moles are still skin cells. So imagine you have an area of skin, and some part of it is “mole” cells and some is regular cells. Both parts are sluffing (losing skin cells) at similar rates, and then replacing those cells at similar rates. So the shape and structure of moles might change overtime, but on average they don’t change much because they are “in sync” with the growth/loss of the cells around them.