I just found a large lump under my right arm, just before my breast. I am 45, non-smoker, eat lots of fresh vegetables, some fruits, drink water 90% of the time. I ve taken Prilosec for about 20 years; was too sick during my pregnancy 15 years ago to not have it. It feels like a golf ball. I m a FT Psych/Sociology student, beginning grad school in fall. Is this likely cancer? My father had prostate cancer about 10 years ago; died of a massive heart attack 5 years ago. I am really scared. Christy