A Foreign Office source later said Johnson had held a "very constructive" phone call with her husband, Richard Ratcliffe, who has called on the minister to visit his wife in jail.
Iran exploited Johnson's comments in court as offering new evidence against Zaghari-Ratcliffe and why she was in the Islamic Republic at the time of her arrest.
They said she had been given a mammogram by the prison's gynaecologist, which gave an inconclusive result.
On Sunday both Labour leader Jeremy Corbyn and Mayor of London Sadiq Khan called on May to fire Johnson - who has been under increasing pressure since Iranian state TV claimed that his statements on the plight of the British-Iranian woman imprisoned in Tehran on charges of espionage confirmed her guilt.
British environment minister Michael Gove defended his colleague Boris Johnson on Sunday, saying he was doing a "great job" as foreign minister and Iran should be "in the dock" over a jailed aid worker, not him.
"When he gets to Iran, I want him to meet Nazanin face to face".
A specialist who examined her believes they are benign but should be monitored because Mrs Zaghari-Ratcliffe has a family history of breast cancer and that the stress she is under could be a contributory factor. Ms Zaghari-Ratcliffe was employed by the Thomson Reuters Foundation when she was arrested by Iran's Revolutionary Guard last April while visiting her parents with her two year-old daughter, Gabriella.
"Nazanin has been complaining of sharp stabbing pains in her breasts for some months - her breasts have been painful since month 5 of her detention".
Mr Johnson said his previous comments were trying to make the point that he "disagreed with the Iranian view that training journalists was a crime".
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Mr Johnson is due to travel to Iran in the coming few weeks and is expected to raise the issue of Mrs Zaghari-Ratcliffe's imprisonment with the Iranian authorities.
Just last week, Priti Patel was forced to resign following revelations she had met senior Israeli officials during a family holiday in the summer, a significant breach of diplomatic protocol.
Ms Zaghari-Ratcliffe said her situation had become a "shambles" under the Foreign Secretary.
"Boris Johnson's cavalier approach to worldwide diplomacy is compounded this morning by Michael Gove claiming he has no idea what Nazanin Zaghari-Ratcliffe was doing in Iran".
It is understood that Mrs Zaghari-Ratcliffe's husband Richard spoke to the foreign secretary on Sunday.
"In that case I take exactly her husband's assurance in that regard", he said.
Gove's answers are likely to create yet more ammunition for the government's critics over its handling of the case.
Mr Corbyn told the Observer Mr Johnson should be sacked as foreign secretary for "undermining our country" and "putting our citizens at risk".