The statement from the diocese Friday revealed George, 75, was treated Wednesday for the condition, though details about the type of cancer were not reported.
"He met with his doctors who reviewed with him test results which showed there were cancerous cells in the kidney and in a nodule, which was removed from the liver," the statement read. "His doctors will work with the Cardinal to plan a course of treatment. The Cardinal will be resting at home this weekend and will be on retreat next week."
In 2006, George underwent a radical surgery to remove his bladder, prostate and a portion of his right ureter due to cancerous growth, the Chicago Sun-Times reported Saturday. Given George's history, Dr. Walter Stadler, a medical oncologist who is not treating the Cardinal, said it's likely he has urothelial or transitional cell cancer.
Dr. Dennis Pessis, a professor of urology at Rush University and president of the American Urological Association said George's doctors likely ran tests to determine the source of the cancerous cells.
"If this is indeed truly a metastatic lesion from the original transitional cell cancer, the prognosis is going to be quite guarded," Pessis said.