My cat has some odd callus's on her back paw pads, what could this be?

Its an off white yellowish color, and grows outward from the edge of the pads. it almost has the feel of a scab being that its very rough but it seems much thicker and stronger.  It doesn't seem to bother my cat except when i want to look at it. Does this pose a health risk to my cat? Should i take her to a vet?

Look up cutaneous horn.  I have something similar on a few of my cats and was advised by vets to snip them off if they bother the cats.  Some are ok with them others I cut off, sometimes the cat gnaws it. 

Vet didn't offer much on exactley why some of my cats have it and others don't considering only 2 were sisters and one is not related as I feared this thing may spread to all my cats when first asked vet.

My one year old cat, Cookie, often has chapped, dry paws. They have white yellowish cracked sores on the paw pads, and I found a cream at my local pet store to help with this. In Cookie's case, I think it was the litter drying out her skin. Now that I'm moisturizing her paws more often, the sores seem to be healing.

Hope your kitty is alright.

I took a cat to the vet for that once. She said it can be caused by the declaw surgery he had four years earlier.

Yes, that would be possible as well. Kate, was your kitty declawed?