A surgical operation to remove part or all of the breast (see BREASTS). It is usually done to treat cancer, when it is commonly followed (and sometimes preceded) by CHEMOTHERAPY or RADIOTHERAPY (see BREASTS, DISEASES OF). There are four types of mastectomy: lumpectomy, quandrantectomy, subcutaneous mastectomy and total mastectomy. The choice of operation depends upon several factors, including the site and nature of the tumour and the patient's age and health. More than half of early stage cancers can be treated with breast conserving surgery rather than total mastectomy. Surgeons and oncologists consult the patient when making the decision about the best course of action. Lumpectomy is done where there is a discrete lump less than 2 cm in diameter with no evidence of glandular spread. A small lump (2–5 cm) with limited spread to the glands may be removed by quadrantectomy or subcutaneous mastectomy (which preserves the nipple and much of the skin, so producing a better cosmetic effect). Lumps bigger than 5 cm and fixed to the underlying tissues require total mastectomy in which the breast tissue, skin and some fat are dissected down to the chest muscles and removed. In addition, the tail of the breast tissue and regional lymph glands are removed. In all types of mastectomy, surgeons endeavour to produce as good a cosmetic result as possible, subject to the adequate removal of suspect tissue and glands.

Breast reconstructive surgery (MAMMOPLASTY) may be done at the same time as the mastectomy – the preferred option – or, if that is not feasible, at a later date. Where the whole breast has been excised, some form of artificial breast (prosthesis) will be provided. This may be an external prosthesis fitted into a specially made brassiere, or an internal implant – perhaps a silicone bag. Reconstructive techniques involving the transfer of skin and muscle from nearby areas are also in use.