I am envious.  I keep hoping for my boobs to grow, but I need to get on HRT again for that.  I was on it for a year, but it did not explode at all during that time. 🙁 🙁 🙁 ;-(

If I were you, this would be something I would discus with my endocrinologist or doctor; any kind of abnormally fast growth should be monitored - especially for cancer.