well best to let it get checked out
things that indicate a cancerous change are
asymmetry - if its not symmetrical it might be canerous
Border- is its 'craggy'
colour - black
defined - smooth or rough...raised or flat (raised and rough = bad)
i think B is meant to be blood actually....if its bleeding or ulcerating.
still its better to be safe...its worth getting checked out and covering up or slapping on the sunscreen.