I am sorry sorry to hear that you parents dog has been diagnosed with cancer, and even sorryier that this thread seems to have been missed.
I do not know if the following link is of any use to you - there is actually a lot of info relating to this illness on the internet, but I do think initially probably not to take too much notice of all you read a be steered by your vet.
regards
DT#

Lymphoma cancer in dogs