The 55-year-old mother-of-four, who is now cancer free, has encouraged other women to ensure they have regular tests after doctors removed her tumour.
Ms Wheeler underwent surgery two times after she was was given the diagnosis in May, she has revealed to the Sunday Times.
She said: “I know the take up of smear tests is way down.
“I know they can save your life.
“If people are willing to listen - as they seem to be - why not say so? Why be afraid?
“I would urge other women to make the time and do the tests.”
Marina told The Sunday Times her four children and her sister had supported her through her illness.
Ms Wheeler married Mr Johnson in 1991 and separated from him in 2018.
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In response to what her reaction was when she was given the diagnosis, she said: “I left thinking, that’s absurd. I have no time for this. Quite apart from everything else I have a book to write.”
She has said that the diagnosis has taught her the “incalculable value of holding close those who you love and trust”.
Due to the cancer diagnosis, Marina has delayed the publication of her book, The Lost Homestead,which is now due to be released at the beginning of next year.
Mr Johnson is now living in Number 10 Downing Street with his new girlfriend Carrie Symonds.
Marina and Mr Johnson are currently going through a divorce.
Around 15% of cervical cancers are diagnosed in women over the age of 65.