Sara Carbonero, 35, made the shock announcement today and explained that doctors have operated on a malignant tumour.
The TV sports journalist says they “caught it in time”, but she still faces months of gruelling treatment.
Sara added: “When we hadn’t yet recovered from one shock, life has surprised us again.
“This time it’s me, that six-letter word I still struggle to write.”
She continued: “I’m calm and confident everything is going to be okay. I know the road will be tough but will also have a happy ending.
“I have the support of my family and friend and a great medical team.”
“I take advantage of this moment to ask that my journalist colleagues show the respect and understanding they have always shown me, especially in these difficult and delicate times for me and my family.”
Sara was filming in Tarifa in southern Spain when former Real Madrid goalkeeper Casillas, 38, suffered his heart attack on May 1.
He had recently signed a new contract with Portuguese club FC Porto – but is now reportedly out for the rest of the season.
The legendary keeper is said to be “out of danger” but was rushed into emergency care.
Casillas’ former teammate Sergio Ramos sent three “praying hands” emojis and tagged him on Twitter.
And Real Madrid winger Gareth Bale said “get well soon my friend”, sharing a picture of him with Casillas.
Sara, who has two sons with her husband, helped organise his 38th birthday yesterday before discussing her own health battle.