Cancer was the last thing on Melissa Donnini’s mind when she was diagnosed with stage 3 rectal cancer. She was only 42 years old.

“I was absolutely shocked,” she said. “You are thinking it’s not as serious as it is, and then you find out what’s involved.”

Donnini underwent radiation and chemotherapy before having surgery to remove her rectum, anus and sigmoid colon. She now has a permanent colostomy.

After her diagnosis, Donnini found out she has Lynch syndrome, a genetic predisposition that increases her risk for different types cancer. While Donnini has answers for her early onset of cancer, not all young patients do.

The incidence of colorectal cancer is declining in older people, but it is increasing in the younger population. A new report released by the American Cancer Society predicts that every day this year, 49 new cases and 10 deaths will occur from colorectal cancer in people under 50 years old. For a large majority of those, the cause is still a mystery. Researchers are looking into the role obesity, diet and the gut microbiome may play in the disease.

In the 1980’s the median age of colorectal cancer diagnosis was 72. By 2016, the median age decreased to 66, meaning half of all diagnoses now occur in people age 66 and younger. The rise in incidence of the disease is most dramatic in people under 50. That rate has been increasing since the mid-1990’s, rising by 2.2% per year between 2011 and 2016.

The American Cancer Society recently recommended that screening for colorectal cancer start at age 45. However, since the U.S. Preventive Services Task Force is sticking with its recommendation that screening start at 50, many insurance companies will not cover the screening for an average-risk person until that age.

“Nobody thinks at a young age to get a colonoscopy,” said Donnini. “That’s why I tell everyone to go get checked if you are having any gastrointestinal issues. You know your own body and you know when something isn’t right. In my case, I kept blowing it off and I had no one to tell me it could be cancer because you just don’t think of those things.”