think of it this way, it is proberly just fatty lumps, but like i said better to be safe than sorry. how old is he? if it is something serious then it is up to you whether or not he goes through an opperation. my dog was put under anaesthesia when he was 12 years old to have a dental, he only had 1/2 the premed and had heart monitors on him. i was on work experience at the time so i watched over him, that was very scary and he woke up fine, the vet said my dog george was the fastest dog to wake up that hed ever seen!

try not to worry too much, it could be nothing!