High-grade serous ovarian cancer (HGSOC), the fifth-deadliest cancer among American women, is thought by many scientists to often be a fallopian tube malignancy masquerading as an ovarian one. A new study suggests there is a direct connection and this finding could aid in the development of better treatments for the cancer.

Ovarian cancer is created by the abnormal and uncontrolled growth of cells and it can spread more widely in the stomach through the bloodstream or the lymph system where it can grow here and form secondary tumours.

There are two main types of ovarian cancer. The most common (9 out of 10) is epithelial that affects the lining of the ovaries.   There are several different types of epithelial ovarian cancer including the two most common – serous and endometrioid. Non-epithelial ovarian cancer is much less common. These include germ cell cancers that form from the cells in the ovary that make the eggs. These usually affect younger women.

Symptoms of ovarian cancer
One of the major problems in diagnosing ovarian cancer is that there are very few, if any, symptoms in the early stages which is why it is known as the ‘silent killer’.  Late detection is one reason why ovarian cancer is notoriously difficult to treat and the American Cancer Society estimates that 22,000 women in the United States are diagnosed with HGSOC each year, and 14,000 die of it. Worldwide, the incidence approaches 200,000 women with 115,000 deaths each year.

If there are symptoms, they can include stomach pain or a bloated feeling that can be confused with irritable bowel syndrome (IBS). Ovarian cysts and non-cancerous growths also cause the same symptoms as ovarian cancer.

Other symptoms include:
• loss of appetite
• unexplained weight gain
• swelling of your abdomen (tummy)
• pain during sex
• changes in bowel or bladder habits
• rarely, abnormal vaginal bleeding

Causes of ovarian cancer
We do not know Doctors don’t know precisely what causes ovarian cancer, but there are some things that seem to make it more likely. It’s more common in women who live in developed countries and for those who have gone through the menopause.  Other factors that have an impact include being on hormone replacement therapy (HRT) – particularly for longer than five years – endometriosis, being overweight (in pre-menopausal women) and
starting your periods early and having the menopause late.

Impact of the new research
Dana-Farber scientists have developed a laboratory model that mimics the process by which fallopian tube cells may turn into cancer cells that appear to have come from the ovaries. Their demonstration that this process can happen in the lab is powerful evidence that it does happen in patients, throwing new weight behind the theory that HGSOC begins, in fact, in the fallopian tubes and not in the ovaries as was previously believed.

This previous belief was founded on examinations of fallopian tubes surgically removed from women with a genetic predisposition to ovarian cancer and areas of the tubes adjacent to the ovary often had patches of cells that were predecessors of serous cancers. But to convincingly show that these cells are the source of high-grade serous ovarian cancer, the scientists needed to trace each step of the disease’s development and believe that their model provides that kind of demonstration.

The origins of HGSOC have been so difficult to track down because of the insidious nature of the disease. Ovarian tumors often establish themselves without producing any warning symptoms and so by the time the disease is discovered, the ovaries can be so overrun with cancer that adjacent sections of the fallopian tube are obscured, making them difficult to examine under a microscope.  Dana-Farber researchers created a laboratory model for studying the lining of the fallopian tubes by using tissue from women who had had their fallopian tubes removed for reasons unrelated to cancer.  Thus they were able to establish a model that mirrors the structure and function of normal fallopian tube tissue in the body.

Studies such as these will help us identify different types of high-grade serous ovarian cancer, as well as possibly discover biomarkers — proteins in the blood — that signal the presence of the disease. Ultimately, the model will enable researchers to test potential therapies to determine which work best in each type of the disease.