Updated April 28, 2015.

If my surgeon cuts into my breast tumor, instead of around it, won't that spread the cancer?

Surgery does not spread breast cancer, but this myth may have started when surgery was done in less than sanitary or poor hygiene conditions. In the 1700s, the rate of survival for breast cancer surgeries was 2 out of 60, 2 years after surgery. Patients may have inadvertently been infected either by unsanitary surgical instruments or by other fluids nearby during the procedure.

This would have increased their physical distress and weakened their ability to fight off infections as well as cancer.

Alternatively, surgeons who were working before the advent of good medical imaging techniques (X-ray,mammogram,ultrasound) may have discovered metastasis only after making the incision which revealed the actual size and condition of a tumor.

By the 1800s, medical practitioners were better aware of how diseases were actually spread through the body. Practices of sanitation as well as sterilization of the surgical area and instruments were put into place, and the rate of survival from surgeries began to improve.

Cancer spreads (metastasizes) through the blood system, the lymph system, or by invading the tissue which is nearest the tumor.