When teens get colorectal cancer, it’s often an aggressive form of the disease

Jo Henderson was 17 when she was diagnosed with advanced colorectal cancer . It came after months of symptoms — stomach pain, bloating, constipation — and months of testing.

“I was expecting a gluten allergy, lactose intolerance,” said Henderson, now 18, of Seekonk, Massachusetts. “Literally anything but cancer.”

Colorectal cancer in people younger than 20 is exceptionally rare: People like Henderson are about one in a million , and account for fewer than 100 cases per year in the United States. But a new study found that most cases of colorectal cancer in kids and teenagers are aggressive, and often diagnosed at advanced stages.