Marcia Wallace, best known for her roles as teacher Edna Krabappel on The Simpsons and Carol Kester on The Bob Newhart Show, died at the age of 70.

A 28-year breast cancer survivor, Wallace had reportedly been gravely ill lately, though the exact cause of her death has not been revealed yet.  The Simpsons producer Al Jean expressed his crew’s sadness over Wallace’s passing in a statement issued to Entertainment Weekly,

“I was tremendously saddened to learn this morning of the passing of the brilliant and gracious Marcia Wallace.  She was beloved by all at The Simpsons and we intend to retire her irreplaceable character.”

Wallace is not the first cast member of The Simpsons to pass away, resulting in the retiring of the character.  Lawyer Lionel Hutz and actor Troy McClure haven’t been seen in a new episode since 1998 after the death of Phil Hartman, and Lunch Lady Doris was retired in 1995 after Doris Grau passed away, but made a brief return in 2006 with another actress doing the voice.  Al Jean also admitted that he and other producers had recently been discussing killing off a long-running character, as they had in the past with Bleeding Gums Murphy and Maude Flanders, though Wallace’s Edna Krabappel was not one of the considered characters.  Wallace was awarded an Emmy for her voice work as Edna Krabappel in season 3 for the episode “Bart the Lover”, where Bart discovers that Edna had posted a personal ad and begins writing her fake love letters, later feeling regret after Edna waits over three hours on a fake date.

Wallace was diagnosed with breast cancer in 1985, later beating it and becoming an advocate for early detection procedures, winning the Gilda Radner Courage Award in 2007 for her work in Cancer awareness.