Biden's 'last known' prostate cancer screening was over a decade ago, as questions mount over diagnosis

President Joe Biden's last known prostate-specific antigen (PSA) test was in 2014, as questions rise about how much his cancer has spread and why it wasn't caught earlier. 

"President Biden's last known PSA was in 2014. Prior to Friday, President Biden had never been diagnosed with prostate cancer," a Biden spokesperson told Fox News. 

The PSA test is a blood test used primarily to screen for prostate cancer. The test measures the amount of prostate-specific antigen (PSA) in the blood, according to the Mayo Clinic. 

PSA is a protein produced by both cancerous and noncancerous tissue in the prostate, a small gland that sits below the bladder in males.

The former president's prostate cancer has been characterized by a Gleason score of 9 (grade group 5) with "metastasis to the bone."

This story is breaking. Please check back for updates.