so stem cells undergo mitosis, but often it is because they are replacing cells that die off- so while they are multiplying, the net number of cells really doesn't change.
for example
the basal cell layer of your epidermis- constantly dividing via mitosis. if you just started digging ditches for a living, and you were developing callouses, then you would add cells faster than you slough them off- hyperplasia. if you are just normal, you add and slough at the same rate and therefore its just plain old regeneration.
sound about right?