Cancer is very common in cats with white ears and also occurs fairly commonly
on the nose of white cats. On ear tips, the best treatment is to remove
the external portion of the ear as far away from the cancer as is possible.
Even though it radically changes the appearance of the affected cats, this
is a fairly simple surgery and not very risky. It is worthwhile to consider
this even if there is evidence of the cancer in other places, I think.
There is some evidence that radiation therapy can be useful in slowing
the progress of squamous cell carcinoma and if that is available in your
area, you might consider it. Unfortunately, this is an aggressive form
of cancer and often it will recur despite aggressive surgical removal of
the visible tumor. Despite this, I really think it is worthwhile to have
surgery done. It makes cats more comfortable and does seem to prolong their
life.