Don't worry yourself too much! There were times when I had exact symptoms for different medical problems. I worried, researched it (it was actually a good thing.. now I know what to look for) and asked the doctor. And if it is cancer, there are still lots of cancer survivors, especially if you catch it early. My grandma had breast cancer and it seemed to have gone away.

I worried myself sick when we found out about Kai's lump on his leg. The vet said it was possible it was a cancerous tumor. I cried til I couldn't breathe. I gained nothing out of it except feeling miserable for days. So don't worry TOO much! Get it checked out if you're really concerned.