Baltimore Orioles outfielder Trey Mancini revealed in a Players' Tribune essay on Tuesday that he had been diagnosed for Stage 3 colon cancer.

The 28-year-old Mancini says he will be undergoing chemotherapy treatments for the next six months and is unlikely to play in 2020.

A native of Winter Haven, FL, Mancini underwent a procedure in March to remove a malignant tumour on his colon.

"When I went in for an endoscopy and colonoscopy, the doctors told me that they were really expecting to confirm that I had celiac disease, which is found in your small intestine," Mancini said. "When the anesthesia put me under, I believed everything was going to be okay."

Mancini, whose father was diagnosed in 2011 with Stage 2 colon cancer, wrote that he began to wonder about a cancer diagnosis before his doctor revealed one.

"He started by eliminating all the possible things it could have been," Mancini said. "I was still woozy from the anesthesia, but before he even said the word cancer I was thinking to myself, There's no way that he's about to say what I think he's about to say. And then he said it: They had found a malignant tumor in my colon."

A four-year pro out of Notre Dame, Mancini appeared in 154 games last season, batting .291 with 35 home runs, 97 runs batted in and an .899 OPS.

Mancini began his current treatment on April 13.