The "SportsCenter" host was first diagnosed with cancer in 2007, when an emergency appendectomy revealed a malignant tumor. He underwent chemotherapy again in 2011.
The 47-year-old Scott joined ESPN in 1993. He quickly became popular for signature phrases such as "Boo-yah!"
He tweeted: "Cancer wants to re-appear..picked the right guy cuz I HIT HARD all day long!!"
On Monday, Scott tweeted "I'm back in the fight. C reared its head again. Chemo evry 2 weeks, but I'll still work, still work out."
In 2011, Scott announced on Twitter that he was undergoing chemotherapy for cancer, but he did not disclose more details.
The Associated Press contributed to this report.