Yes, dogs can get cancer. Cancer is a mutation of genetic material that effectively “breaks” the normal functions of a cell, causing the cancer cells to multiply uncontrollably, and invade healthy tissue. Theoretically this can occur in anything with cells- even plants have been recorded as having tumours. Some organisms have a natural resistance to cancer- look up the naked mole rat; it’s not pretty, but it is a very interesting animal!
Yes, all animals or anything with cells can harbour a mutated gene that could lead to a cancer spreading. Animal cell function although is not Panarea of expertise for me so I will differ to Sinead on this!