CNN) -- ABC news anchor Peter Jennings has been diagnosed with lung cancer, his colleagues were told Tuesday.
ABC News President David Westin informed the staff of ABC News in a memo saying Jennings, 66, would begin outpatient treatment and expects to continue to anchor "World News Tonight."
"There will be good days and bad, which means some days I may be cranky and some days really cranky," Jennings told ABC News employees in an e-mail, according to The Associated Press.
The text of the memo from Westin is as follows:
"This morning, Peter Jennings told his senior staff at World News Tonight that yesterday afternoon he was diagnosed with lung cancer. ... He will begin outpatient treatment next week here in New York. It's both Peter's and my expectation that he will anchor World News Tonight during the period of treatment to the extent he can do so comfortably; but, we should also expect him to be off the broadcast from time to time, depending on how he feels.
"Charlie Gibson, Elizabeth Vargas, and others will be substituting for Peter as necessary and when their other responsibilities permit.
"All of us at ABC News have watched over the years as Peter has led us on various assignments with strength and with courage. We've done our best to support him in these endeavors. Now, Peter's been given a tough assignment. He's already bringing to this new challenge the courage and strength we've seen so often in his reporting from the field and in anchoring ABC News.
"I know that all of us will give him every bit of support that he needs and asks for. Peter will once again lead the way, but we will stand with him at every turn."
Jennings has been the sole anchor of "World News Tonight" since 1983. He was part of a group of anchors, with Frank Reynolds and Max Robinson, for several years before that. He also anchored ABC's evening news show in the 1960s, when he was in his late 20s.
