Doctors say they want to investigate the case of a British man with HIV who apparently became clear of the virus, reports BBC.
Two Sunday newspapers report Scotsman Andrew Stimpson, who lives in London, was diagnosed as HIV-positive in 2002, but found to be clear in October 2003.
Chelsea and Westminster Healthcare NHS Trust, which carried out the tests, have asked him to undergo more tests. Stimpson did not take any medication for HIV.
HIV experts say his case could help to reveal more about the disease.
A statement from the trust said: "We regret this has been a distressing time for Stimpson and are happy to discuss any aspect of his care with him. This is a rare and complex case. When we became aware of his HIV negative test results, we offered him further tests to help us investigate and find an explanation for the different results. So far Stimpson has declined this offer. It is therefore difficult for us to comment any further."
There have been anecdotal accounts before from Africa of people shaking off the HIV virus, but the evidence in this case, as reported in the News of the World and the Mail on Sunday, appears to be conclusive, BBC said.
Stimpson said: "There are 34.9 million people with HIV globally and I am just one person who managed to control it, to survive from it and to get rid of it from my body. For me that is unbelievable - it is a miracle. I think I'm one of the luckiest people alive."
Stimpson told the newspapers that he became depressed and suicidal after being told he was HIV-positive but remained well and did not require medication.
Some 14 months later he was offered another test by doctors, which came back negative.
He sought compensation but has apparently been told there is no case to answer because there was no fault with the testing procedure.
Chelsea and Westminster Healthcare Trust have asked to conduct more tests on Stimpson both for his benefit and for other patients.
He has told the media he would do anything he could to help find a cure.
Aids expert Dr Patrick Dixon, from international Aids group Acet, said the case was "very, very unusual".
"I've come across many anecdotal reports of this kind of thing happening in Africa, some quite recently, but it's difficult to verify them," he told BBC News 24.
"You have to be rock-solid sure that both samples came from the same person, no mix-up in the laboratory, no mistakes in the testing, etc. This is the first well-documented case."
He said the case was important because "inside his immune system is perhaps a key that could allow us to develop some kind of vaccine".