This is a fascinating article on an extremely important potential discovery in how cancer operates... and shows the potential dark side of stem cells:

A spate of new discoveries about the basic biology of cancer is pushing researchers toward an astonishing conclusion: For decades, efforts to cure the disease may have targeted the wrong cells.

Current therapies treat all cancer cells the same. They're aimed at shrinking tumours on the basis that the various cells within them all have similar powers to spawn new cancers and spread destruction.

But mounting evidence suggests that cancer's real culprits -- the roots of perhaps every tumour -- are actually a small subset of bad seeds known best to the world as stem cells.
...
Abnormal stem cells have now been identified as the engines driving certain cancers of the blood, breast, brain, bone and prostate. And today, two research groups -- one in Canada and another in Italy -- report in an advance online publication of the journal Nature that they have pinpointed aberrant stem cells as the source of colon cancer, the second leading cause of cancer deaths.

It's a rather long article, but well worth your time.