There a few possibilities. As he's been getting them for 10 years, I think we can probably rule out Squamous Cell Carcinoma in his paws, amongst other cancer options, but non-cancerous possibles include:
Cutaneous horn - Which may be linked to some serious issues, but can be benign. They can be removed surgically and should be looked at by a vet for underlying causes.
Fibroma - Which is benign, but you can remove it surgically if it's causing discomfort. A biopsy would be needed to confirm, though I don't think it's common to get on the pad.
Hyperkeratosis - In cats, this could be caused by pemphigus foliaceus resulting in increased keratin at the foot pad, but there could well be other reasons for it (people are calling it "horned paw"). Also should have vet intercession to deal with, if necessary.
There are some more dangerous causes as well though, as I noted, the history would suggest extremely unlikely. It may also be none of the above as well, it's really hard to say, but increased keratin from one reason or another seems pretty likely.
On the long story short front... You shouldn't remove it yourself.