Scientists have grown new prostate glands in mice, in another advance for stem cell technology.
The team from San Francisco were able to isolate single cells with the ability to generate an entire prostate.
The technique, reported in the journal Nature, could shed light on how prostate tumours develop.
However, any thoughts it could lead to transplants in men who have had the gland removed to beat cancer have been played down.
The prostate is found near the bladder, and helps make and expel semen, but is a common source of cancer, especially in older men.
A quarter of all new cancers diagnosed in men are prostate cancers, and 10,000 die from the disease every year in the UK.
The US researchers were able to track down a type of stem cell which divides to form the different cell types in the gland.
When these mouse stem cells were transplanted back into mice, they developed into entirely new glands.
However, this does not mean that entirely new prostates can be fabricated for men who have lost them.
Any new gland would have to be not only connected back to the urethra - the tube which carries urine from the bladder to the outside of the body, but also somehow to the complex system of nerves controlling its activity.
Even if this complex surgery were possible, many doctors would argue that the benefits of having the gland as an older man do not entirely justify it.
Prof Robin Lovell-Badge, MRC National Institute for Medical Research, said: "Of course the main clinical problem with the prostate gland is not a need for additional ones, but their overgrowth, which often turns to prostate cancer.
"However, knowing the identity of these stem cells may eventually allow the development of therapies that specifically target these cells in a way that keeps them under control."
Professor Malcolm Alison, Professor of Stem Cell Biology at Barts and The London School of Medicine and Dentistry, agreed, saying that, in older men, the prostate tended to be a cause of "serious medical problems".
"However, it is a widely held view that cancers originate from normal stem cells, so this discovery will be a significant boost to prostate cancer research aimed at understanding how this deadly disease develops."
John Neate, the chief executive of The Prostate Cancer Charity, said: "This study is an important piece in the jigsaw of our understanding of the role that stem cells play in the prostate.
"It gives very clear evidence of the existence of stem cells in the prostate of mice. Scientists think they may work in a similar way in humans.
"Much research is being undertaken to unravel the role stem cells may play in the development of cancer and how they may respond differently to treatments."