The 'Grease' star found out she had breast cancer in 1992, but decided to keep the news from her then eight-year old daughter, who was dealing with the loss of her best pal and associated the disease to death.
"She had lost her best friend to cancer six months before and it seemed the wrong thing to tell her... because to her she associated cancer with death," Contactmusic quoted John, as saying.
But eventually Lattanzi realised about her mother's problem through her schoolmates.
"Some kids went up to her (and said), 'Ah, your mum has cancer.'" John told U.S. news show Entertainment Tonight.
"She came running home from school and said, 'Why didn't you tell me...?' I said, 'Because I didn't want to worry you,' and she said, 'Mum, I would've taken care of you,'" she added.