How fast would a lipoma on the top of a foot grow to be considered a "fast growing" lipoma?

Noticeable = fast: I don't know a speed per hour/day/week/month but if you notice it, it's faster than expected. If it hurts or even is uncomfortable - have it examined and removed if the provider thinks it is a good idea. Once cooler weather requires shoes, the procedure would be more annoying. Also, w/ OA any avoided discomfort is good. So, have it checked now would be my suggestion.

Excisinal biopsy: I would set the time limit at one month. however I would not use the time limit criteria to determine whether a growth needs to be removed or not. my suggestion is, have what is thought to be a lipoma removed.