EastEnders character Jean Slater will "face one of her toughest times yet" in a storyline that sees her diagnosed with ovarian cancer, the BBC has said.
The soap said it has worked closely with Macmillan Cancer Support.
Actress Gillian Wright, 58, who plays Jean, said: "It's an honour and a huge responsibility to be taking on such an enormous issue, affecting so many women and their families.
"I'm aware of the impact such stories can have. It's important we treat the issue of cancer diagnosis and treatment with huge sensitivity, dignity and respect.
"I hope the storyline helps awareness of the disease and is supportive to those that are affected."
The soap's senior executive producer, Kate Oates, said: "Jean's diagnosis will impact every aspect of her life, including her family, her friendship groups and her mental health, and I know an actor of Gillian's calibre will approach the story with great truth and depth.
"The Slaters are an amazing ensemble family, full of complex and well-drawn characters, and this story is a completely fresh subject for them to tackle. I know they'll do it justice and in turn raise awareness of such an important issue that affects so many people."
Georgina Wiley, treatment and recovery adviser at Macmillan Cancer Support, said: "Being diagnosed with cancer can turn someone's whole world upside down and stories like Jean's can genuinely save and improve lives.
"It's been a privilege to work with EastEnders to ensure the plot and the language used in the scripts are a true reflection of the impact that cancer can have.
"We want all the 'real-life Jeans' watching to know that we are here to help. Our free support line is open seven days a week, 8am-8pm on 0808 808 00 00."
The soap said Jean's storyline will unfold in the coming weeks.
By Kerri-Ann Roper, Press Association Entertainment Editor