Sex and the City star Cynthia Nixon has revealed she is a breast cancer survivor.

The 42-year-old actress, who plays Miranda Hobbes in the hit TV show, was diagnosed 18 months ago - but has kept it quiet.

In an interview on US show Good Morning America she admitted: "I felt scared".

Brave Cynthia revealed she even had the surgery on a Sunday - so she would not miss even one performance of the Broadway play she was in at the time, adding: "That's just the way I am," Nixon admitted.

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Cancer battle: Sex and the City star Cynthia Nixon has revealed on a US television show that she is fighting breast cancer

Big screen time: The star is set to hit the big screen after reuniting with the cast of the hit TV show for a big screen version, Sex and the City: The Movie

The actress spoke out about the life-changing event, and for the first time about her relationship with lesbian lover Christine Marinoni, who she admitted was hit hard by the cancer crisis.

Cynthia revealed: "My girlfriend was very scared.

"She was the one doing the eating. She was in a panic - she was just trying to calm herself down any way she could."

The actress said she always thought she would get the disease because her mother had battled it when she was just 12.

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Scared: Cynthia, seen here with her partner Christine Marinoni, said the shock news hit her girlfriend hardest, and that they were both very 'scared'

Cynthia was given the news that a small tumour had been found after a mammogram. But she said: "I realised it had been found early so they could get right on with it."

The lumpectomy was followed by six weeks of radiation treatment.

She said her own crisis made her re-evaluate how Sex and the City used breast cancer for a storyline, insisting: "I think it was beautiful. Like, leave it to Samantha to make a party out of cancer!"

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Cynthia spoke out about her cancer battle on US show Nightline, after becoming an official ambassador for a breast cancer organisation,

But while Samantha fought a very public battle on the show, Cynthia deliberately kept her ordeal out of the public eye.

"I didn't really want to make it public while I was going through it. I didn't want paparazzi at the hospital, things like that", she said.

Together with partner Christine, the couple broke the news to her two children - Samantha, 11 and Charles, 4, from her previous relationship with their long-time companion Danny Mozes.

"I told them, 'They found some breast cancer in my right breast, it's very small, it's very early, I'm going to have an operation and they are going to take it out, and then we are going to have six and a half weeks of radiation and this is like what grandma went through - and I'm gonna be fine," she said.

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Cynthia and her co-stars Kristin Davis, Sarah-Jessica Parker and Kim Cattrall in the highly anticipated film of their hit show

Cynthia, also revealed that her children call them both the women 'mom'. She said: "They love her, they call her mom.

"My son is very funny: sometimes he says mum and it's obvious he means both of us - or either of us. He's just 'Mom' and whoever answers is fine."

The actress is now an official ambassador for Susan G. Komen for the Cure, the world's largest breast cancer organisation.