should I tell my dad?

I live with my mom and I have recenetly discovered a lump on my breast. I have a history of breast cancer in the family and so my mom took me to the doctors. they were concerned because it was fairly large for a cyst and they said if it doesn't go away by the end of my period to come back. it is still here and my period has been done for a week or so. I have another doctors appointment in September. should I tell my dad or just not have him worry about it till I know what it is for sure?