Lumpectomy is typically performed on an outpatient basis and rarely requires hospitalization. Patients are usually instructed not to eat or drink for 6 to 12 hours before surgery to ensure the stomach is empty. Prior to the procedure, the surgeon will meet with the patient and any family members to discuss the surgery, questions or concerns.

Lumpectomy is performed with either a local anesthetic (numbs the surgical site) or general anesthetic (puts the patient to sleep temporarily). The surgeon makes an incision large enough to remove both the tumor and a portion (margin) of healthy tissue surrounding the cancer. This helps ensure that no cancer cells are left behind in the breast. Usually, the margin size is around 1 centimeter (less than 1/2 inch). This tissue is sent to a laboratory for analysis by a pathologist. 

In addition, the surgeon typically samples the lymph nodes under the armpit to see if the cancer has spread. Most often, this is done by removing the sentinel lymph node, the first lymph node to which a tumor drains. This is known as a sentinel lymph node biopsy. The sentinel lymph node is found before surgery by injecting a radioactive dye near the tumor. In some cases, cancer of the sentinel lymph node will be obvious, and the surgeon will remove additional lymph nodes to prevent metastasis.

However, in other cases the cancer will not be evident until after a pathologist performs laboratory testing on the sentinel lymph node. If biopsy reveals cancer in the first node, a second surgery can be scheduled to remove additional lymph nodes.

Sentinel lymph node biopsy is now frequently used instead of a lymph node sampling method known as an axillary lymph node dissection. The axillary procedure removes several lymph nodes and involves more extensive surgery. An axillary lymph node dissection may still be performed if a sentinel lymph node biopsy reveals cancer and it becomes necessary to remove additional lymph nodes.

All of the incisions performed during the lumpectomy will be closed with stitches that either dissolve or are removed by a healthcare professional. A drain tube may be placed in the breast to remove build-up of fluid during the recovery time. Adhesive strips may be placed over the incisions to help hold them in place during healing.

The lumpectomy procedure usually takes less than two hours and is frequently performed on an outpatient basis. However, in some cases a hospital stay will be required, particularly for patients who also have several lymph nodes removed. If the patient has received general anesthesia, recovery may take several hours and the patient can be driven home after she is awake and alert.

Because a portion of the breast has been removed, there may be a change in the appearance of the breast. A noticeable scar, dimpling or asymmetry of the two breasts may occur. There also may be a scar under the arm where the lymph nodes have been removed. Unsatisfactory cosmetic results are more likely in women with large tumors or who have tumors that are relatively large compared to breast size.