cat tooth poking out

i have just noticed that one of my cats 'fangs' is really long. she is approximately 13 years old, eating fine although a little skinny which i think is just her age. is this something is should be concerned about. You can see on this pic a black spot on her lower lip, this is now where the long tooth is.

Answer by Kate
oh how strange, I have not come across this before as there teeth are normally kept worn down by eating some dry kibble food. It could perhaps be that she has a slight deformity in her jaw, which has made the tooth jut out. All I can recommend is that you have it looked at by a vet to put your mind at rest at least.