(CNN) Sen. John McCain has been diagnosed with glioblastoma, an aggressive brain tumor, Mayo Clinic doctors tell CNN. Unlike other brain tumors that start in the body and spread to the brain, glioblastoma starts in the brain or spinal cord. The senator underwent surgery to remove a blood clot on Friday at the Mayo Clinic in Phoenix, Arizona. Lab results from the surgery confirmed the presence of glioblastoma. Glioblastoma is the most common of all malignant brain tumors, representing 15.4% of all primary brain tumors, according to the ABTA, who estimate there will be over 12,000 cases before the end of 2017.

Source: CNN July 20, 2017 08:28 UTC