My female Guinea pig Pearl is about 6 years old and has developed a dark brown growth on her leg that sticks out vertically. It is more long than wide, and is about the size of a very small raisin (except it's skinny not circular). I’d say it’s soft and it does not seem to be causing her pain. She’s eating and drinking normally, but I became concerned when I noticed the growth. Does anyone have an idea of what this might be?
Is it hard and crusty? Firm? Soft? Are hairs growing out of it? Has it bled at all?
It is also remotely possible it is sebaceous material but I would expect the skin would break and not be raised like this is.
Here are your pics:
I would be tempted to break the skin of it at the highest point (stop if you see any blood) to determine if there is any sebum present - though the safest thing is to see a vet, who will likely be quite familiar with growths like this.
p.s. one technique veterinarians use is removal of a growth using a ligature to cut the blood supply. This is done, for example, with "extra" toes (polydactyly), as in this picture:
More about this condition: