We're just starting to understand the different types.
General categories are er+, er/pr/her2+, er-/her2+, and er/pr/her2-. Her2+ tend to be more aggressive but can be counteracted w/herceptin
. Triple neg are also more aggressive but some of these are very chemosensitive. Genomic analysis/microarrays allows further subdividing. The environment of the tumor in the body is also likely critical.