When I biopsy a mole and send it to be looked at by a pathologist, I am looking to see whether or not it is a melanoma (cancer of moles). Even if it is not a melanoma, a mole can be still concerning enough to need further treatment.
The pathologist will look at the cells of the spot and determine if any of the cells have “atypia” (abnormality). The degree of this atypia will determine how concerning the spot is. There are four categories of atypia. The mole could be entirely normal, or it could have mild, moderate or severe atypia. Normal or mild means we don’t need to do anything further to the spot. Severe means the spot is close enough to melanoma we need to remove it so it doesn’t turn into a melanoma. Moderate atypia means we want to remove the spot completely to make sure it’s gone, but we are not terribly worried about it.
If you have had a mole with moderate or severe atypia, it makes sense to be checked every year or so.