Former prime minister Baroness Thatcher is “absolutely fine” in hospital after undergoing a minor operation, a spokeswoman said.
The 87-year-old was admitted to hospital on Thursday and was kept in overnight last night after having a growth removed from her bladder.
Downing Street said Mr Cameron wished Baroness Thatcher "a speedy recovery".
"She is absolutely fine," the spokeswoman said of the ex-premier, who has suffered some ill health in recent years.
Baroness Thatcher was not well enough to join the Queen for a lunch with former and serving prime ministers as part of the Diamond Jubilee this summer.
And two years ago she missed an 85th birthday party thrown for her by Prime Minister David Cameron at 10 Downing Street.
In October she was sufficiently well, however, to mark her 87th birthday with lunch at a restaurant in London's exclusive St James's district with her son Mark and his wife.
Her health was thrust into the global spotlight this year when Meryl Streep starred in a controversial Hollywood film about her.
The Iron Lady drew criticism from Mr Cameron and others for concentrating on the dementia she has suffered after a series of small strokes. Meryl Streep won an Oscar for the role.
Lord Tim Bell, the leading PR and advertising figure who was a close adviser to Baroness Thatcher, said she was expected to need several days of recuperation.
It could well mean she will spend Christmas in hospital, where she has been accompanied by her daughter Carol. Her son is believed to be on holiday overseas.
Lord Bell said the former politician had been in some pain earlier in the week and was sent by her doctor to hospital where it was decided the operation was required.
It was a short procedure using what was described as "minimally invasive surgery", he said.
"She's fine," he added.
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