Mastectomy means removal of the breast. By modern convention this is a relatively conservative procedure and does not involve removal of any chest wall muscle as used to be standard 25yrs ago.
Mastectomy remains the gold standard for disease free survival, although this has been challenged in the last 15yrs by Wide Local Excision and radiotherapy, which is as good with proper selection.
The complication rate is low and the pain associated with surgery is not great. The major problems tend to be related to the axillary procedure (armpit), which is recommended in most cases.
Surgery is performed under general anaesthetic and hospital stay is 2 to 4 days usually, depending on the drain.
Reconstruction of the breast is a far more major undertaking, the surgery taking in the region of four hours, involves a High Care Unit often, more potential complications and about a week to 10 days in hospital.