What is the likely hood these polyps are cancerous?

I am in my early 20s and have been have pain/etc. in my abdomen. I had a colonoscopy and they removed some polyps (between 12-15cm) while they were checking everything out. Is it normal for people my age to have polyps? Also, what makes me really worried is that colon cancer runs in my family. Both my grandmothers had it (one caught in stage 2 and other stage 4 I believe) so I am a little nervous. The more I look on the internet for answers, the more confused I get. I have a follow up appointment scheduled, but the wait is really taking a toll on me. Any help would be appreciated. Thanks.