The tennis legend discovered she had the disease in February. She admits initially feeling terrified, but is now confident she will beat it.
"I cried, I was shocked, I was devastated. Physically I could not think or move, I was useless." Martina told People magazine. "It knocked me on my a*s, really. I feel so in control of my life and my body, and then this comes, and it`s completely out of my hands. The emotions took so much physical strength out of me, I didn`t realise how much impact physically this has on you."
The 53-year-old found out about the cancer after a mammogram detected a problem in her left breast.
Martina has ductal carcinoma in situ (DCIS) which is a non-invasive form of the cancer. It was found in her milk ducts, and had not spread.
"It was the best-case scenario you could imagine for detecting breastcancer," said Martina`s friend Dr. Mindy Nagle.
Martina is due to start a sex week radiation therapy course next month, and has had a lumpectomy.
"I went four years between mammograms," she told the publication. "I let it slide. Everyone gets busy, but don`t make excuses. I stay in shape and eat right, and it happened to me. Another year and I could have been in big trouble."