Sykes told Ellen DeGeneres that she's lucky to be alive because the cancer was only discovered by chance after she'd undergone a breast reduction surgery.
"I went for the reduction. I had real big boobs and I just got tired of knocking over stuff. Every time I eat… Oh lord. I'd carry a Tide stick everywhere I go. My back was sore so it was time to have a reduction," Sykes joked.
She continued: "It wasn't until after the reduction that in the lab work, the pathology, that they found that I had DCIS [ductal carcinoma in situ] in my left breast. I was very, very lucky because DCIS is basically stage-zero cancer.
"So I was very lucky… But cancer is cancer. I had the choice of, you can go back every three months and get it checked. Have a mammogram, MRI every three months just to see what it's doing. But, I'm not good at keeping on top of stuff. I'm sure I'm overdue for an oil change and a teeth cleaning already."
Even though the cancer was only found in one of her breasts, Sykes decided to have a double mastectomy to ensure that the disease will never recur.
"I had both breasts removed… because now I have zero chance of having breast cancer," the comedian said. "It sounds scary upfront, but what do you want? Do you want to wait and not be as fortunate when it comes back and it's too late?"
Her full interview will air on The Ellen DeGeneres Show on Monday.
> Wanda Sykes came out to parents on phone
> Wanda Sykes: 'Donald Trump is after attention'
Watch a clip from Wanda Sykes's stand-up routine below: