Her2 positive is estrogen based cancer. It feeds off the estrogens and It's aggressive and can get into your lymphnodes. According to my onc. Now is the time to have this kind, not that anyone plans this. With tamoxifen and other drugs out, tamoxifen blocks the receptors from the cancer and herceptin is fairly new as well in which helps stop this type of cancer. Nothing is 100 percent but with these new drugs, the outcome is greater.

There Are 4 her proteins in your breast. Her2 is the one that makes your cells multiple quickly. Her2+ means the cancer has hooked onto those cells.

To take a step back, when you're a diagnosed, your cancer will be tested for what "feeds" it (at least that's how I think of it). They test to see if it is Progesterone responsive (PR), estrogen responsive (ER) or HER2 responsive (HER2). What this tells the doctor is what fuels your cancer to grow. You can be positive to all 3, or negative to all 3 (also known as 'triple negative') or any mix in between.

HER2 is just a protein that your body naturally produces. For some reason, certain cancer cells feed off this protein and grow faster when it is present.

Historically, HER2+ was a bad thing. Because it is one of the most aggressive cancers and because there was no long term therapy to treat it. But in the 90s (or early 2000s), someone discovered Herceptin, which is a mild form of chemo that is proven to be very effective in treating this form of cancer. AND the side effects with it are extremely minimal (your hair even grows back). So most HER2+ ladies are given Herceptin for a full year, once every 3 weeks. This helps minimize risk of recurrance, which (prior to Herceptin) was most common in the first two years.

So the bad news is that HER2+ means you have an aggressive form of cancer, and they will treat it aggressively (which typically means AC and Taxol, so 4-5 months of chemo). However, the long term outlook is much better than it was 15 or so years ago.

Good luck!