Hi, User1987 , I, too, am sorry to hear about your Mom’s pain.
When my Dad was on Keytruda, he never complained our “outright” pain. But, since his passing, I have learned that he wasn’t the most forthcoming with me. It seems that he didn’t want me to worry.
I agree with Melanoma , that you or she should contact the oncologist. They are your best resource for letting you know if this is a side effect of her Keytruda, or whether it could be something she needs to see her GP about.
Thanks, Elsie13 For the tag.