Sore by dogs nail

Question
I took my dog (a 4 year old lab/mastiff mix) to the vet for a small growth next to his toe nail yesterday.  I had done some research on the internet and came up with three possible diagnoses, a cyst, an abscess, or the dreaded word CANCER.  When I took him in (it was a new vet I'd never seen before) she poked around and looked at it for a long time and then told me it is usually cancer when a dog has a sore on a toe like that.  She gave me antibiotics and an Elizabeth collar to keep him from licking it and told me to wait 10 days to see if it clears up.  I have started soaking his foot in warm epsom salt baths (in case of abscess) b/c I read about that treatment on the internet.  She seemed extrememly sure that it is going to turn out to be cancer even though he's had persistent skin problems (pink wet rashes, dandruff, wart-like growths, rough elbows) his whole life.  Basically what I want to know is should I have insisted that she do a biopsy before waiting 10 days to do anything...is 10 days going to make a huge difference if it is cancer?  Are the cancers that manifest themselves in the epithelial tissue usually really fast to metastasize?  Can they do a biopsy without completely removing the toe (a skin scraping or a needle)?  What other questions should I ask the vet if it does not clear up because during his appointment I was frozen by the "c" word?  Thanks.  

Answer
You have asked alot of questions that unfortunately can only be answered on the basis of a biopsy.  We had a dog the other day with a nasty looking tumor on its foot and I was sure that it was a malignancy.  It was ugly, but it was a benign tumor and taking it off was curative. Most tumors on the dog are benign.  There are a few malignant tumors that are bad like melanomas or squamous cell carcinomas.

If it is an abscess or a cyst, doing the things you are doing should resolve it, but if it grows fast or ulcerates, then have it looked at again and perhaps do the biopsy then.