Ryan said in a statement released by the team a lump on his neck had been diagnosed as a squamous cell carcinoma -- a treatable form of the disease.
The 60-year-old GM said doctors determined it had not spread beyond his neck and were optimistic he will return to good health.
"Understanding the need to focus on treatment and recovery, I will not be in Fort Myers (Fla.) as we commence spring training," Ryan said, adding he was "highly confident" in assistants Rob Antony and Mike Radcliff and Twins Manager Ron Gardenhire to prepare for the team for the 2014 season.
The Twins said Ryan will be treated at the Mayo Clinic in Rochester, Minn., and a Twin Cities oncology clinic.
2014: The Year in Music [PHOTOS]