Yes they can
We had a Bouvier de Flanders,she was about 10 yrs old when got skin cancer,all benign -about 7 of them.She began losing weight,vet put her on special food & took alot of tests-refused to admit she could have cancer. Less than a year later we had to put her down for cancer.
I should clarify this to state: when asked the vet if internal cancer possible he stated if they have tumors on outside they can't possibly have them inside.
Live & learn,got a new vet of course.