BALTIMORE (AP) — Orioles outfielder Trey Mancini is undergoing chemotherapy for stage 3 colon cancer and expects to miss the season if major leaguers return this summer.

Mancini had a malignant tumor removed shortly before turning 28 on March 18. He has been undergoing chemotherapy since April 13.

“My treatment will take six months — every two weeks for six months,” Mancini wrote in a story posted Tuesday on The Players Tribune. “If baseball returns in 2020, it will probably be without me.”

Stage 3 means is defined as a cancer that has grown into nearby tissue or lymph nodes. Stage 4 is defined as a cancer that has spread to other parts of the body.

Mancini acknowledged he likely would never have realized he had cancer if not for an examination by the Orioles.

“I am so lucky,” he wrote.

Mancini received an exam at spring training that revealed his iron levels were low. He figured colon cancer was a remote possibility because of his age.

“I was only 27. No way I had that,” he wrote. “My dad had had stage 2 colon cancer in 2011, but he was 58 then. We just thought I was way too young for me to have it.”

A colonoscopy revealed the tumor, and Mancini had surgery March 12.

Mancini is certain he will be able to play again but unsure of when.

“Even when I’m doing chemo, I can work out and do some things. So, whenever the time comes for me to come back to baseball, I’ll be ready,” he wrote. “But I just want to make sure that I am physically fine before I go out there and start trying to perform again at a major league level.”

Mancini had a career year in 2019, his third full season with Baltimore. He played in 154 games and batted .291 with 35 homers and 97 RBIs even though the last-place Orioles lost more than 100 games for the second year in a row.