path report and her2+ status

I am confused by some of the info on my path report and how it relates to being her2+. Here is the info: Histopathologic grade 5, Nottingham score 5pts grade I, er+pr+, aneuploid, Elston tumor grade I. her2 3+. I pretty much understand er/pr status, but not how the grades and scores relate to aggressiveness and her2 status. I am stage II, 5 of 14 nodes with microscopic node involvement. Any insight?