Black spots on ears

my diabetic cat has been on transdermal tapapzole applied to the ears for a few months now for hypert. i've noticed that her ears have small black spots on the outside and look kind of rough (crinkly) around the edges. have you eever hear of cats getting cancer from using tapazple on the ears or having other ear problems from it. can black spots on the outside of the ears mean cancer? i have an older cat who has black sposts on her ears that have been diagnosed as age spots but my diabetic cats ears have gotten the spots and the crinklyness since using the tapazole.
thank you.

 

Geez...I sure don't know. Could you call your vet and see if that is a side effect?
I do know my all white cat, Abigail, will get black crusty spots on the outside of her ears. Vet does not think it is cancer because he can remove them(pick them off) and says it looks healthy underneath. White cats are more prone to get skin cancer, but it is still uncommon. My vet did say that since I was treating the ears with a cream that it could have been dirt getting caught in the cream making it black and crusty or her hair follicles were clogged. Just suggestions. Can you remove the black stuff pretty easily?