Ovarian cancers were previously thought to begin only in the ovaries, but recent evidence suggests that many ovarian cancers can actually start in the cells at the far end of the uterine (fallopian) tubes. The ovaries are mainly made up of three kinds of cells. Each type of cell can develop into a different type of tumour:
- Epithelial tumours start from the cells that cover the outer surface of the ovary. Most ovarian tumours are epithelial cell tumours.
- Germ cell tumours start from the cells that produce the eggs.
- Stromal tumours start from structural tissues, cells that hold the ovary together and produce the female hormones, oestrogen and progesterone.
Some of these tumours are benign never spread beyond the ovary. Malignant or borderline ovarian tumours can spread to other parts of the body and can be fatal.
Epithelial Ovarian Tumours
Epithelial ovarian tumour start at the outer surface of the ovary. These tumours can be benign, not cancer, borderline, low malignant in potential or malignant cancer.
Benign Epithelial Ovarian Tumours
Epithelial ovarian tumours that are benign don’t spread and usually don’t lead to serious illness. There are several types of benign epithelial tumours such as serous cystadenomas, mucinous cystadenomas, and Brenner tumours.
Borderline Epithelial Tumours
The two most common types are atypical proliferative serous carcinoma and atypical proliferative mucinous carcinoma. These tumours were previously called tumours of low malignant potential (LMP tumours). These are different from typical ovarian cancers because they don’t grow into the supporting tissue of the ovary (called the ovarian stroma). If they do spread outside the ovary, for example, into the abdominal cavity (belly), they might grow on the lining of the abdomen but not into it. These tumours grow slowly and are less life threatening than most ovarian cancers.
Malignant Epithelial Ovarian Tumours
Cancerous epithelial tumours are called carcinomas. About 85-90% of malignant ovarian cancers are epithelial ovarian carcinomas. These tumour cells have several features that can be used to classify epithelial ovarian carcinomas into different types. The serous type is by far the most common and can include high grade and low grade tumours. The main types include mucinous, endometrioid, and clear cell.
- Serous carcinomas (52%)
- Clear cell carcinoma (6%)
- Mucinous carcinoma (6%)
- Endometrioid carcinoma (10%)
Ovarian cancer ranks fifth in cancer deaths among women, which account for more deaths than any other cancer of the female reproductive systems.
A woman’s risk of getting ovarian cancer during her lifetime is about 1 in 78.
Her lifetime chance of dying from ovarian cancer is about 1 in 108.
This cancer mainly develops in older women.
About half of the women who are diagnosed with ovarian cancer are 63 years or older. It is more common in white women than African-American women. The rate at which women are diagnosed with ovarian cancer has been slowly falling over the past 20 years.
Factors that Increase the Risk of Ovarian Cancer
The risk of developing ovarian cancer increases with age. Ovarian cancer is rare in women younger than 40. Most ovarian cancers develop after the menopause. 50% of all ovarian cancers are found in women 63 years or older.
Obesity has been linked to a higher risk of developing many cancers. It is thought that obese women with a body mass index of 30 or over have a higher risk of developing ovarian cancer but not necessarily the most aggressive types. Obesity also negatively affects the overall survival of a woman with ovarian cancer.
Having children later or never having a full-term pregnancy.
Women who have had their first full term pregnancy after the age of 35 or never carried a pregnancy to term have a higher risk of ovarian cancer.
HRT After Menopause
Women using oestrogens alone or with progesterone after menopause have an increased risk of developing ovarian cancer compared to a woman who has never used hormones.
Family History of Ovarian Cancer, Breast Cancer or Colorectal Cancer
Ovarian cancer runs in families. The ovarian cancer risk is increased if mother, sister or daughter has had ovarian cancer. Risk gets higher than more relatives one has. Increased risk for ovarian cancer also comes from the paternal history.
Family history of other types of cancers such as colorectal or breast cancer is linked to an increased risk of cancer. This is because cancers can be caused by inherited mutations such as the BRCA1 or BRCA2 genes.
Hereditary Nonpolyposis Colon Cancer
These patients also have a higher risk of ovarian cancer. Peutz–Jeghers syndrome leads to an increased risk.
Fertility treatment with the IVF seems to increase the risk of type of ovarian tumours known as borderline or low malignant potential. Research on this is unclear.
Past History of Breast Cancer
If you have had breast cancer you may also be at an increased risk of developing ovarian cancer.
There is no apparent increase in ovarian cancer overall if smokes but there is a link to an increased risk of the mucinous type.
Factors with Unclear Effects on Ovarian Cancer Risk
Androgens, such as testosterone, are male hormones. There appears to be a link between certain androgens and specific types of ovarian cancer, but further studies of the role of androgens in ovarian cancer are needed.
This is unclear if there is an increased risk. The overall increase is likely to be very small. Research is required.
A diet high in vegetables or a low fat diet may reduce the rate of ovarian cancer.
Factors That Can Lower Risk of Ovarian Cancer
Pregnancy and Breastfeeding
Women who have been pregnant and carried to term before the age of 26 have a lower risk of ovarian cancer than the women who have not. This risk goes down with each full-term pregnancy. Breastfeeding may lower the risk even further.
Patients taking oral contraceptives have a lower risk of ovarian cancer. The risk is lower the longer the pills are used. This lower risk continues for many years after the pill is stopped. Interestingly, other forms of birth control such as sterilisation and short use of IUDs has also been associated with a lower risk of ovarian carcinoma.
Hysterectomy without removing the ovaries also seems to reduce the risk of getting ovarian cancer.
Can ovarian cancer be found early and screened for?
Only about 20% of ovarian cancers are found at an early stage. When ovarian cancer is found early, 94% of patients live longer than five years after the diagnosis. There are two types of tests, which are available:
Transvaginal ultrasound scan
CA125 blood test
The CA125 blood test measures the amount of protein called CA125 in the blood. If the CA125 is close or above the upper limit of normal it should be repeated. There is an unreliability about the test, but sequential rises may alert to the possibility of ovarian cancer formation.
It is suggested that if the CA125 is normal, it could be repeated in one year.
Here at The London General Practice, our full health screen includes a CA125 blood test and, although the result isn’t fully validated, any concern is reviewed and a referral for further screening or gynaecological review is arranged immediately.
Dr Paul Ettlinger
The London General Practice