Jeannie Hayes anchored the NBC affiliate's noon news and its Sunday morning community affairs program, 13 Cares.
Originally from Indiana, Hayes graduated from Marquette University in Milwaukee and got her first job with WREX in 2005.
She leaves behind her parents and two sisters, the WREX website said.
"Out of respect to her family and Jeannie, WREX will air tributes to Jeannie this evening on 13 News starting at 5:00 p.m. The pictures, stories and memories are endless, so we will try to compile the best in the way that we know Jeannie would want us to," the station's website said.
According to WREX, Hayes learned she had the illness Tuesday and died late Thursday night at OSF St. Anthony Medical Center in Rockford.
"I've always loved writing stories, and I love to talk to people," Hayes wrote in her WREX bio. "Working in TV news is the perfect combination of the two. 'The Oprah Winfrey Show' also inspires me, because I love the idea of using TV to teach people."