Veteran "Good Morning America" entertainment editor Joel Siegel, 56, is undergoing cancer surgery for the third time on Wednesday, he announced on Monday's edition of the a.m. show. He is to undergo removal of a growth on his right lung, he said. Last year he developed one on his left lung, which surgeons successfully removed. More than three years ago Siegel had colon cancer. And, in 1982, he dealt with the death of his first wife of six years, the former Jane Kessler, who had a brain tumor. Facing this new hurdle, Siegel -- a Los Angeles native who started his career as a joke writer for onetime Presidential candidate Robert F. Kennedy -- says that his greatest concern is how to explain his illness to his 3-year-old son, Dylan. On Tuesday's "GMA" he led a roundtable discussion on how families should discuss health issues together. "We all face our own mortality every day," said Siegel, "but we aren't forced to think about it. I'm forced to face it. I don't want Dylan to see me afraid. I don't mind him seeing me sad. I don't mind him seeing me cry. But I don't want him to see me afraid."