You should worry....I, too, had 19 negative nodes, but there was lymphatic invasion noted...so the cancer left the original site...where did it go? No negative nodes tends to put people to sleep as far as not worrying....I'm not saying you should obsess, but there's nothing wrong with keeping up with things. And, if your cancer was Her2 positive, I believe you should worry more, regardless of what the onc. says!