New research, published on April 26, 2010, in the journal in PLoS ONE, revealed that researchers from Fox Chase Cancer Center (Philadelphia, PA, USA) have uncovered early tumors and precancerous lesions in cysts that fold into the ovary from its surface, called inclusion cysts. "This is the first study giving very strong evidence that a substantial number of ovarian cancers arise in inclusion cysts and that there is indeed a precursor lesion that you can see, put your hands on, and give a name to,” stated Jeff Boyd, Ph.D., chief scientific officer at Fox Chase and lead author on the study, which also involved colleagues at Memorial Sloan-Kettering Cancer Center (New York, NY, USA). "Ovarian cancer most of the time seems to arise in simple inclusion cysts of the ovary, as opposed to the surface epithelium.”

Clinicians and researchers have been looking for early ovarian tumors and the precancerous lesions from which they develop for years without success. In this study, Dr. Boyd and colleagues used a combination of conventional microscopy and molecular approaches to reveal the early cancers.

"Previous studies only looked at this at the morphologic level, looking at a piece of tissue under a microscope,” Dr. Boyd said. "We did that but we also dissected away cells from normal ovaries and early stage cancers, and did genetic analyses. We showed that you could follow progression from normal cells to the precursor lesion, which we call dysplasia, to the actual cancer, and see them adjacent to one another within an inclusion cyst.”

To learn where and how the tumors arise, the team examined ovaries removed from women with BRCA mutations, who have a 40% lifetime risk of developing ovarian cancer, and from women without known genetic risk factors. In both groups, the researchers discovered that gene expression patterns were considerably different in cells in the inclusion cysts compared to the normal surface epithelium cells, including increased expression of genes that control cell division and chromosome movement.

Moreover, when the investigators used a technique called fluorescence in-situ hybridization (FISH), which can be used to identify individual chromosomes in cells, they noticed that cells from very early tumors and precursor lesions frequently carried extra chromosomes. In fact, the team found that 9% of the normal cells isolated from the cysts had extra chromosomes, even though the tissue appeared completely benign under the microscope. By contrast, virtually none of the cells isolated from the surface of the ovary, which was previously believed to be the site of early ovarian cancers, carried extra chromosomes.

With these new data on the origin of ovarian cancer, Dr. Boyd and others can now begin to develop screening tests, perhaps based on molecular imaging, which could be utilized to detect early ovarian cancers in asymptomatic women.

Related Links:
Fox Chase Cancer Center
Memorial Sloan-Kettering Cancer Center