<s>[INST] question about NF-- I have a medium sized plexiform neurofibroma on my thigh. it never bothers me at all until i get my period. That first day or 2 of my cycle, it hurts A LOT. it helps to take ibuprofin and put the heating pad on it. Why does it only hurt then? [/INST] Hi.This is a good question and a good history.Your history is self-explanatory. This swelling is hormonal dependent, meaning  the changes in this particular time occurs as the swelling is responding to hormonal changes that occur every month.I would suggest you to check for the swelling , whether it is really a neurofibroma. </s>