A plastic surgeon will help you determine if reconstruction makes sense for you. They can add implants to round out a breast that has had a lumpectomy or they can use implants to re-create your breasts following a mastectomy. Some patients are candidates for a skin, or a skin + nipple sparing mastectomy depending on the location of your tumor(s). If this is not an option for you, you will find that these surgeons are magicians and the work they do using skin graphs and tattoos can make your new breasts look very "normal".
If you are having a mastectomy, there are several routes you can go for reconstruction if you choose to have reconstruction - there are pros and cons to each route so make sure to ask the surgeon to explain each option they feel is available to you in detail and again, make the decision that is best for you - talking to others who have had the same procedure if you want to help you decide:
Direct to Implant
Expanders then Implant - The nice thing about expanders is that you can decide the size you want your implants based on how full your expanders get, but if you can go direct to implant, that means less sur gery for you.
Lat Muscle - Use your lat muscle as your implant
Stomach Muscle - User your stomach muscle as your implant
If you get implants - Make sure you are clear with your surgeon how big you want your implants to be and also talk about smooth versus textured implants. There have been some rare localized cancer occurrences that have been linked to textured implants but they are very rare. Just make sure to talk to your surgeon about your options and decide what is the best choice for you.
You can also have a "fat transfer" done to take fat from another part of your body to round out your breast area. This can be done either during your initial surgery or may need to be done as a follow-up porcedure/surgery.