Nazanin Zaghari-Ratcliffe, the British-Iranian woman being held in Iran, has seen a specialist after finding lumps in her breasts, her husband has said.
Richard Ratcliffe also expressed concern that his wife appeared to be “on the verge of a nervous breakdown”.
She was arrested during a visit to Iran in April 2016, accused of trying to overthrow the regime, which she denies.
Cabinet ministers Boris Johnson and Michael Gove have been accused of bungling the UK’s handling of the case.
Mrs Zaghari-Ratcliffe’s family have issued a statement about her condition, saying she had been “complaining of sharp stabbing pains in her breasts” for more than a year.
They said she had been given a mammogram by the prison’s gynaecologist, which gave an inconclusive result.
The full details of the allegations against Mrs Zaghari-Ratcliffe have never been made fully public.
She maintains the purpose of her trip to Iran was to visit family.