About Hollings Cancer Center

Comprehensive breast care program

MammoSite Procedure

Diagram of the Mammosite ProcedureTreatment with MammoSite is a two-stage process: balloon placement and radiation delivery.

MammoSite Placement

After the surgeon removes your tumor, an uninflated MammoSite balloon is gently placed inside the tumor cavity through a small incision. A portion of the catheter will remain outside of your breast (Figure 1). The MammoSite can be placed either during your lumpectomy surgery or up to 10 weeks after surgery in a separate procedure.

Once in place, the balloon is inflated with fluid to fit snugly into the tumor cavity. The balloon remains inflated for the entire time you are receiving radiation therapy (Figure 2).

After the MammoSite is placed, the breast is bandaged and you may go home.

MammoSite Radiation Therapy

Next you will visit a radiation oncologist - a specialist in treating cancer with radiation - who will take images of the MammoSite in your breast and determine the amount of radiation your breast will need to receive. Once your treatment prescription is established you may begin radiation therapy.

During radiation therapy, you will visit the radiation oncology office twice a day. The portion of the MammoSite catheter remaining outside of your breast will be connected to a computer-controlled machine.

A tiny radioactive source (seed) will then travel from the machine, through the catheter, and into the inflated balloon inside your breast. The source will remain in the balloon for about 10 minutes while it delivers radiation to your breast (Figure 3). Once you have received the prescribed dose of radiation, the source is retracted back into the machine. No radiation remains in your body between treatments or after the final treatment is over.

Usually on the same day as your last radiation session, the MammoSite balloon will be deflated and easily removed (Figure 4).

Frequently asked questions about MammoSite

Information provided by Cytyc Corporation makers of Mammosite.

Mammosite Web site (opens in a new window)


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