In an interview with the Mail on Sunday, the 51-year-old broadcaster said she would have a mastectomy next month in order to remove a six centimetre tumour.
Surgeons will also take tissue from her lymph nodes to establish whether the disease has spread to other parts of her body.
Bradbury’s diagnosis followed a mammogram she booked in July on an annual recall, having last year found a lump which proved to be a cluster of benign micro-cysts.
While the tumour was described as “sizeable”, doctors believe the cancer cells have not yet spread to the breast tissue, meaning she may not need chemotherapy.
Bradbury told the paper she was sticking to the positives: “It is quite good on the scale on cancers. But as with all tumours, until you are in there you never know.
“As it is I am going to lose my breast. I trust that one day I will look down on it and think that was the fight of my life and I have the ultimate battle scar to prove it.”
The Countryfile presenter urged other women to regularly check themselves for breast cancer and not to be afraid to seek help.
“We must, must, must check ourselves and seek help,” she said.
“Being scared of a diagnosis could be the thing which kills you. So learn what to look for and check, check, check.
“Doctors are experts but only you can press a lump, know how it feels and think you should do something about it.”