"The first day I was like, 'Oh, OK, no big deal ... maybe it’s something that just got on my T-shirt,' he said. "Second day I looked and the same thing, and I was like, 'Eh ... interesting.' Then on the third day I was like, 'What is this? I wonder what this is.'"
Knowles said a couple of days went by, and he didn't see any discharge, but on the fifth day, he saw another small drop of blood. He told his wife, and they soon made a doctor's appointment.
"When I had the blood on my T-shirt initially, I didn’t think it was breast cancer," Knowles said. "My mind went a lot of places. My mind went to what medication I was on, because different medications might have caused some sort of discharge ... and then I thought, just because of the risk factor, that it could be breast cancer and I would go get a mammogram."
It turned out to be stage 1A breast cancer. He immediately got surgery and underwent testing for the BRCA gene mutation.
Knowles said he's still getting his test results back, including for a prostate exam. He had one of his breasts removed.
"I am going to get the second breast removed in January, because I want to do anything I can to reduce the risk," he said. "We use the words 'cancer-free,' but medically there’s no such thing as 'cancer-free.' There’s always a risk. My risk of a recurrence of breast cancer is less than 5%, and the removal of the other breast reduces it down to about 2%."
Knowles said he daughter, Beyonce, immediately went to get tested once he informed her of the diagnosis.
According to the American Cancer Society, 2,670 new cases of invasive breast cancer will be diagnosed in men this year. Black men tend to have a worse prognosis compared with white men.
Knowles came forward to raise awareness of male breast cancer and to encourage other men to get tested and examined.
"I need men to speak out if they’ve had breast cancer," Knowles said. "I need them to let people know they have the disease, so we can get correct numbers and better research. The occurrence in men is 1 in 1,000 only because we have no research."
Read more about Knowles' breast cancer revelation on GMA.com.