Mark Grishaber was diagnosed with leukemia "in the past week," according to an email blast sent by the school's alumni foundation Monday. View Full Caption DNAinfo/Heather Cherone

CHICAGO — Taft High School principal Mark Grishaber was diagnosed with leukemia "in the past week," according to an email blast sent by the school's alumni foundation Monday.

The principal will stay on leave "for up to four weeks" while he undergoes chemotherapy treatments, Richard Winge, a member of the Taft High School Foundation, wrote in Monday's email.

"There are many types of Leukemia and sometimes people can live for years with it but the cancer may lead to other health problems," Winge continued.

On Nov. 18, Grishaber suddenly announced he'd go on medical leave for "three to four weeks," telling students that the "best way for you to help me get healthy and back to work is to be the most successful students you can be."

Winge's Monday letter implored teachers, alumni and students to send personalized get-well cards to the school so that they can be delivered to Grishaber's home.

"He's the Principal of our Alma mater and has done many very good and great things for Taft," Winge wrote. "It would be lovely if he received hundreds of cards and letters from alumni and friends."

Grishaber has been principal of the school since 2014. Last month, Taft received CPS' second-highest academic rating for the second consecutive year.

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