http://www.ctv.ca/CTVNews/Health/20100909/endometriosis-100909/ TORONTO Canadian researchers have isolated a genetic mutation that appears to link two types of ovarian cancer with endometriosis, a common gynecological condition in women. Endometriosis is the abnormal growth of cells that form outside the uterus, attaching themselves to such structures as the ovaries, fallopian tubes and even the outside of the intestines. Endometriosis often has no symptoms, but in some women the growths can cause pain and lead to infertility. In a study published in this week's New England Journal of Medicine, researchers at the Ovarian Cancer Research Program of B.C. found that a mutation that turns off the ARID1A gene may be a preliminary event in the transformation of endometriosis into one of two types of ovarian cancer. Those cancers -- called clear-cell carcinoma and endometrioid carcinoma -- represent the second and third most common types of ovarian tumour, said principal researcher Dr. David Huntsman, a genetic pathologist at the B.C. Cancer Agency. Together, they account for one-quarter of all ovarian cancer cases in North America and an even higher proportion of ovarian tumours among Asian women. The genetic mutations were found in 46 per cent of ovarian clear-cell carcinomas and in 30 per cent of endometrioid carcinomas. But Huntsman stressed that having endometriosis does not mean a woman will develop ovarian cancer. "Endometriosis is a very common condition and there have been (research) papers over the years suggesting that women with endometriosis are at a slightly higher risk of developing clear-cell carcinoma and endometrioid carcinoma," he said from Vancouver. "However, the risk is low for any individual woman with an endometriosis." "One thing we really don't want to happen is for every woman who has endometriosis to suddenly be terrified that they're going to get cancer." Lead author Kim Wiegand, a graduate student in Huntsman's lab, first noticed multiple mutations involving the ARID1A gene. In all, the research team sequenced DNA from more than 600 ovarian tumour samples collected from scientists worldwide. "When we first saw these mutations we were very excited because ARID1A has several functions that made it a potential cancer gene, yet mutations in this gene have never been identified before in ovarian cancer," said Wiegand. The detection of the common genetic mutation could lead to better treatments for these forms of ovarian cancer, which are not well understood, said Huntsman, director of OvCaRe, a partnership program between the B.C. Cancer Agency and the Vancouver Coastal Health Research Institute. "Our discovery has shown that loss of ARID1A may be a very early event in this transformation (to cancer), and we hope to be able to use the discovery to develop tools to determine which women with endometriosis may be at increased risk," he said. "It may be that some women could be treated a little more aggressively to remove that risk." Dr. Andrew Berchuck, director of gynecologic oncology at Duke University Medical Center in Durham, N.C., called the research "a major scientific breakthrough." "This discovery also sheds light on how endometriosis predisposes to the development of these cancers," he said in a statement. "The novel insights provided by this work have the exciting potential to facilitate advances in early diagnosis, treatment and prevention of endometrioid and clear-cell cancers, which account for over 20 per cent of ovarian cancer cases."