There are certain people on whom the mastectomy surgery is recommended by the doctor to be performed like:
If the tumor in your breast is larger than about 5 cm. Some tumors that are lesser than this measure might also need the surgery performed to remove it.
If other procedures like a lumpectomy (this takes a certain amount of tissue from your breast) are not suitable for you because you have small breasts, then the procedure of mastectomy is advised.
If you have previously undergone lumpectomies and the tumor or cancerous cells have not been completely removed by other procedures.
If radiation treatment is not an option for you because of previous radiation attempts in the same breast, or because you are suffering from a form of connective tissue disease (like rheumatoid arthritis or lupus) or if you are pregnant.
If you do not want to undergo daily radiation treatments.