Surgery 

Depending on the staging and type of the tumor, just a lumpectomy (removal of the lump only) may be all that is necessary, or removal of larger amounts of breast tissue may be necessary. Surgical removal of the entire breast is called mastectomy.

Lumpectomy techniques are increasingly utilized for breast-conservation cancer surgery. However, mastectomy may be the preferred treatment in certain instances:

• Two or more tumors exist in different areas of the breast (a "multifocal" cancer).

• The breast has previously received radiation (XRT) treatment.

• The tumor is large relative to the size of the breast.

• The patient has had scleroderma or another disease of the connective tissue, which can complicate XRT treatment.

• The patient lives in an area where XRT is inaccessible.

• The patient is apprehensive about the risk of local recurrence after lumpectomy.

Standard practice requires the surgeon to establish that the tissue removed in the operation has margins clear of cancer, indicating that the cancer has been completely excised. If the removed tissue does not have clear margins, further operations to remove more tissue may be necessary. This may sometimes require removal of part of the pectoralis major muscle, which is the main muscle of the anterior chest wall.

During the operation, the lymph nodes in the axilla are also considered for removal. In the past, large axillary operations took out 10 to 40 nodes to establish whether cancer had spread. This had the unfortunate side effect of frequently causing lymphedema of the arm on the same side, as the removal of this many lymph nodes affected lymphatic drainage. More recently, the technique of sentinel lymph node (SLN) dissection has become popular, as it requires the removal of far fewer lymph nodes, resulting in fewer side effects. The sentinel lymph node is the first node that drains the tumor, and subsequent SLN mapping can save 65-70% of patients with breast cancer from having a complete lymph node dissection for what could turn out to be a negative nodal basin. Advances in Sentinel Lymph Node mapping over the past decade have increased the accuracy of detecting Sentinel Lymph Node from 80% using blue dye alone to between 92% and 98% using combined modalities. SLN biopsy is indicated for patients with T1 and T2 lesions (<5cm) and carries a number of recommendations for use on patient subgroups.