Friend found this in cat’s armpit (warning: gross)

[jahzara]

She said the top part is hard like a fingernail or claw, sort of.
She said it was shifting around a bit but didn’t seem to be bothering her so she pulled it out.
The bottom white part is slightly sticky like when you pull a hair out of a follicle. And it’s soft and flexible so thinks it was in her skin.

 

[Caspers Human]

It’s probably something called a “cutaneous horn.”

Cutaneous Horn: Pictures, Removal, Causes, and More

It‘s basically just a hardening of the skin.
They happen in humans and animals.

If there are no signs of injury, bleeding or infection it’s mostly harmless.

If it was me, I’d call the vet at the next convenient opportunity and ask their opinion. Save the piece in case the vet wants to examine it. If the vet doesn’t want to look at it, throw it away.

Beyond that, I don’t think it’s much to worry about.