Mucinous ovarian cancer

What is mucinous ovarian cancer

Mucinous ovarian cancer (MOC) is a rare form of ovarian cancer. It is diagnosed in about three per cent (three in 100) of cases, so around 200 people a year in the UK.

Mucinous ovarian cancer is different from the more common, high grade serous form of epithelial ovarian cancer. MOC is most often found in people aged under 40, unlike high grade serous epithelial ovarian cancer which is mostly found in older people, aged over 50.

It tends to form a large tumour and so may cause symptoms and be detected before it has spread. This results in 80 per cent of cases (80 in 100) being diagnosed early, at stage 1, so it can often be treated by surgery only, without using chemotherapy.

MOC sometimes affects a single ovary so fertility sparing surgery, which preserves the unaffected ovary, may be possible.

Not all mucinous tumours are cancers, some are found to be benign.

What causes mucinous ovarian cancer?

Mucinous cancer cells secrete mucus, a thick protective fluid. This type of cell is not normally found in the ovaries, but they are found in the stomach, intestines and inside the inner part of the cervix.

This means that if mucinous cancer is found in an ovary it may have arisen in one of these organs. So, the ovary may be a site of metastasis or secondary cancer, while the source of the mucinous cells (the primary cancer) may be in another part of the body, such as the stomach.

In about 80 per cent of cases (80 in 100) of MOC the tumours arose from another part of the body. This means that only about twenty per cent, (20 in 100) of mucinous ovarian cancer tumours are primary tumours.

MOC does not have the same risk factors as other ovarian cancers, such as age, family history and not having children. The only risk factor that has been suggested in some research is smoking, which is seen as increasing the risk of MOC by a small amount.

How is Mucinous ovarian cancer diagnosed?

People with MOC usually have an undiagnosed abdominal mass that is removed surgically, and a diagnosis is then made. Sometimes there can be significant pain that may come on quite quickly as large masses can twist; this is described as torsion.

There are blood tests that can detect MOC. Carcinoembryonic antigen (CEA) and CA 19-9 are cancer markers that are more likely to suggest the presence of MOC than the one used for other forms of ovarian cancer, which is CA125.

You may then have a trans-vaginal ultrasound (where the ultrasound probe is inserted into your vagina) or a CT scan to investigate the swelling in your pelvis and to look for any other tumours. An MRI scan may also be used to see if the MOC itself is a primary or secondary tumour. This is important to know as treatment may be different for these two types of MOC tumours.

If the MOC tumour is a secondary tumour you may have an examination of your stomach or colon (bowel) using an endoscope, a thin flexible tube with a camera at the top, to find the primary cancer tumour.

Treatment for mucinous ovarian cancer

Surgery

Like most ovarian cancers, the initial treatment of MOC is surgery. If the cancer has been diagnosed early at stage 1 this may be all the treatment you need.

The operation will remove your ovaries, fallopian tubes, womb, cervix and omentum (a fatty layer in the abdomen). Sometimes surgeons will also remove pelvic and para-aortic nodes (glands at the back of your abdomen). They will also examine your appendix as that can be a source of mucinous cancer.

The operation will include peritoneal washing; this introduces sterile fluid into the pelvic area which is then removed to see if it has collected any cancer cells. The surgery aims to remove as much of the cancer as possible and may include peritoneal biopsies being taken.

If your cancer was diagnosed at a later stage, then your surgeons will try to carry out the same operation and aim to remove as much cancer tissue as possible. This means a diagnosis can be made and the cancer’s spread (its stage) can be seen. You can read more about surgery here.

The identification of an ovarian tumour as a MOC is made by a pathologist who will look at the tumour using a microscope. This process can take a week or longer. The information from the pathologist will include the type of ovarian cancer you have, how far it has spread and its grade, which is a measure of how fast the tumour is growing.

Chemotherapy

After surgery you may be offered chemotherapy. This will probably be platinum-based using the drugs carboplatin and paclitaxel (Taxol) which are used to treat ovarian cancer. However, there is little research on using these drugs for MOC.

In 2019 a US study looked at the benefits of using chemotherapy to treat MOC which had been diagnosed early at stage 1 (when the cancer is still contained in the ovaries). It found no difference in outcomes in people who had received the treatment and those who had not.

MOC is known to have a reduced sensitivity to platinum-based chemotherapy compared to other forms of ovarian cancer. This means it is less clear if patients should have chemotherapy after surgery, particularly if the cancer has been found at an early stage.

Chemotherapy should be offered to meet the individual needs of patients and discussed carefully with their clinical team.

You can read more about chemotherapy here.

Treatment in the future

At present there is no evidence of better treatment options for mucinous ovarian cancer than the standard platinum-based chemotherapy drugs used in other forms of the disease.

There have been no successful clinical trials that have only included people with MOC. This has been because very few people are affected, and trials have not been able to include enough patients to produce reliable results.

Some of these trials have tested the use of chemotherapy drugs that are used to treat bowel cancer, which is often mucinous.

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Researchers are looking at the roles of gene mutations that are sometimes present in MOC tumours but are different from those associated with other forms of ovarian cancer. These include KRAS and HER2. Research has found little evidence to suggest that immune-boosting drugs would be effective in the treatment of MOC.

More research is needed, including research on the genetics of MOC.

Gill says:

“When I was first diagnosed, I felt incredibly scared and isolated. I needed to know more about mucinous ovarian cancer to get some control back into my life.I researched as much as I could find, but because MOC is so rare there was very little information. What I did find was often written in medical jargon and hard to understand.

It has been difficult to find a treatment protocol, so I haven’t been able to judge whether I’m getting the best care – which is unsettling. MOC doesn’t respond in the same way to CA125 testing as other ovarian cancers so I’ve had no way to tell if it has recurred, which is a worry.

I’ve had to ask several times to have other blood tests which can work better with MOC, but I do get them now.

I’ve also managed to get in contact with other people diagnosed with MOC which has made me feel more supported.”

Gill was diagnosed in 2017 when she found a lump in her abdomen after experiencing fatigue and bloating. She was treated with surgery.

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