Deanna Favre faces up to five months of chemotherapy but a full recovery is expected, said Bonita Favre.
According to the Sun Herald, Brett Favre learned of the cancer on Oct. 14 and left Green Bay for a day to be with his family before returning to play in the Oct. 17 game at Detroit.
"Brett was relieved to learn that the situation is not as bad as it could have been," Deanna's brother-in-law, Scott Favre, told the newspaper. "We think that they got (all of the cancer) out."
In addition to Casey Tynes' death in the ATV accident, Favre's father, Irv, died in December from a heart attack.
"The family has been through a great deal and we will get through this," Bonita Favre said. "We would like to thank everyone for the prayers and support. We're a strong family and with the help of the Lord, we'll get through this."