CHICAGO (CBS) — The woman who led the first Chicago teachers strike in 25 years could be stepping down.

The Chicago Teachers Union announced Karen Lewis on Friday filed paperwork to retire from her teaching career, but there’s no word on whether she’ll be leaving her post as president of the Chicago Teacher’s Union.

CPS said she would make a decision regarding her future in that role in the next few weeks.

Lewis has been battling brain cancer.

CBS 2’s Derrick Blakley reports on what’s next.

Karen Lewis said she is stepping down because her battle with brain cancer has made it impossible to do her job “at my best.”

She told the Chicago Tribune “I want my members to know that I’m not abandoning them…I will be around to help do things. I’m not disappearing anywhere.”

It was just two weeks ago that the union revealed that the 64-year-old Lewis was back in the hospital for undisclosed surgery.

She’s been fighting brain cancer since 2014, saying today “my plan is to try to get somebody to unseat Rahm. I think we can do better than Rahm Emanuel.”

“He’s murdering schools. He’s murdering good jobs. He’s murdering housing.  I don’t know what else to call him. He’s the murder mayor,” said Lewis of Chicago Mayor Rahm Emanuel in 2013.

Lewis and the mayor have been at odds from the very start.

Their very first meeting lead to profanity. After that it was battle on, leading to the 2012 10 day teacher’s strike. The first in a quarter century.

The cancer diagnosis, Lewis said, hit her hard.

“I was completely shocked.”

Mayor Emanuel said he honored Lewis’ fighting spirit, saying he has seen her drive and tenacity first hand.

Lewis’ full statement via the Chicago Teachers Union:

Given my health challenges, it is unlikely that I will return to my beloved classroom. In light of that, and after much consideration, I recently submitted a retirement request to the Chicago Teachers Pension Fund, ending my tenure as an educator with Chicago Public Schools.

For nearly three decades, I have worked to educate our city’s children and provide them with a foundation for learning that will follow them throughout their lives. In the coming weeks, I will make a determination regarding my role as president of the Chicago Teachers Union and our path forward in fighting for the schools our children deserve.

I am nearing the end of my third term. I remain president today, with a strong leadership team that includes our Vice President, Jesse Sharkey. I will be engaging with my fellow CTU officers and members about our direction forward over the months ahead and will be communicating with our members, allies and the public in the coming days.