Navy, my aunt and great-aunt both went through breast cancer. In the words of my great-aunt (who is in her late 90's and has not only been in remission for over 10 years, but she was recently elected to the New York State Assembly) to my aunt, "Honey, breast cancer is nothing. Beating it is a piece of cake, you'll be fine"
Lumps are very scary things to find. My aunt was 42 when she found a suspicious lump, and when she went to the doctor's and had it checked out, it was revealed to be benign. I don't know if my great-aunt's was benign or not, but I can tell you this....if the lump is benign, treatment is about a year, if not less. The chemo will make you nauseous and when you undergo radiation they will draw all over you with markers that will look like bizarre tattoos, but my aunt said that was the hardest part.
If I were you, unless told otherwise, assume it's benign. Those ones are the easiest to handle. If a 90 something year old woman can look back on breast cancer and say "Oh it was a piece of cake" then I have tremendous confidence in your ability to go "Oh this is nothing. I can beat this"
If it is benign, you can tell your boys that Mommy has something in her boob that isn't supposed to be there, but it will be gone soon. All Mommy will need sometimes is some help, and she might throw up from time to time, but whatever is making her sick will be gone in about a year's time.