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What is the most aggressive type of ovarian cancer?

Ovarian cancer is not one disease but can be made up of different cell clones or types. The subtypes of ovarian cancer differ depending on the type of cell they originated in, response to treatment, and aggressiveness.

Woman on doctors couch holding stomach

Each year, about 1500 Australians are diagnosed with ovarian cancer. Most ovarian cancers are diagnosed at an advanced stage due to a lack of early-stage symptoms and no effective screening test. Some types of ovarian cancer are aggressive and recur or progress quicker; however others can be slow-growing. The most common type of ovarian cancer is epithelial ovarian cancer.

Epithelial ovarian cancer

Approximately 85% of all ovarian cancers are epithelial which originate from epithelial cells that line the surface layer of the ovary. Epithelial ovarian cancer is more common in women over 50 years of age.

There are four different types of epithelial ovarian cancer including serous, endometrioid, clear cell and mucinous.   

Serous

Serous is the most common epithelial cancer type, and it can be divided into:

  • high grade serous ovarian cancer
  • low grade serous ovarian cancer

Serous ovarian cancer is divided into low or high-grade by looking at tissue under a microscope.

High-grade serous ovarian cancer is the most common type of epithelial ovarian cancer, and all other sub-types of epithelial ovarian cancer are considered rare.

High-grade cells grow rapidly, are considered aggressive, and therefore unfortunately are diagnosed at advanced stages and have a worse prognosis. Some high-grade serous ovarian cancers have been found to start in the fallopian tube. These cells then spread to the ovary and grow. Fortunately, high-grade serous cancers often respond to chemotherapy, especially early, when a diagnosis has just been made.

Doctors may refer to low-grade cells as ‘indolent’, which means slow growing. It is rare that low-grade serous cancer will convert to high-grade. Compared to high-grade, low-grade serous ovarian cancers are more resistant to chemotherapy.

Endometrioid carcinoma

Endometrioid is the second most common type of epithelial ovarian cancer and tends to grow slower. These cancers often develop in women with endometriosis. Most cases of endometrioid ovarian cancer are diagnosed at an early stage and are low grade.  Radical surgery is the mainstay of treatment of this ovarian cancer type.

Clear cell

Clear cell ovarian cancer is an uncommon subtype of epithelial ovarian cancer.

Clear cell cancers are more likely to present at an early stage as it tends to present with a large pelvic mass, or deep vein thrombosis (blood clotting). However, they are also one of the more aggressive types of ovarian cancer and progress quickly.

Clear cell cancer patients are more likely to be diagnosed at a younger age, be diagnosed in people of Asian descent, and is also associated with endometriosis.

The treatment for clear cell is the same as for high grade serous ovarian cancer, however chemotherapy is not as effective.

Mucinous

Mucinous ovarian tumours are another rare subtype and can be difficult to diagnose. Tests will be conducted to see if the cancer originated in the ovary, or if it spread there from elsewhere in the body.

Not all mucinous ovarian tumours are cancerous. Mucinous ovarian tumours are classified as benign (non-cancerous), borderline or malignant (cancerous).

Mucinous tumours are usually large, slow growing and tend to remain confined to the ovaries, and when diagnosed early prognosis is good.

Other less common, non-epithelial ovarian cancers include:

  • Ovarian germ cell tumours are rare and begin in the reproductive (egg) cells in the ovary. Cancer Council Queensland reports about 4% of women have this subtype. They normally affect only one ovary and occur often in young and adolescent women under the age of 40. There are further subtypes of ovarian germ cell tumours and most are aggressive. However, they often respond well to chemotherapy and many women will have children following chemotherapy.
  • Stromal (sex cord) tumours are also uncommon, start from structural tissues that support the ovary and produce the female hormones oestrogen and progesterone. They normally occur in women aged 40 to 60 years, and include both benign and malignant types.
  • Small cell carcinoma.This subtype tends to be fast-growing, aggressive and diagnosed in young women, even teenagers. It usually presents with a pelvic mass. This is the rarest form of ovarian cancer with only a few hundred cases reported in the medical literature. I will see a patient with this rare tumour type only every few years.

Tumours that appear to arise from ovarian tissue but in reality are metastatic from elsewhere

Sometimes tumours of the intestinal tract may not be visible themselves but the only sign is an ovarian mass. That’s why sometimes we check the bowel, stomach or we remove the appendix to exclude a primary bowel tumour.

Stages of ovarian cancer

As well as the subtype, the stage of your ovarian cancer will help to determine the most efficient and least harmful treatment.

  • Stage I: Cancer is in one or both ovaries only.
  • Stage II: Cancer is in one or both ovaries and has spread to other organs in the pelvis (uterus, fallopian tubes, bladder or bowel).
  • Stage III: Cancer is in one or both ovaries and has spread beyond the pelvis to the lining of the abdomen (peritoneum) or to nearby lymph nodes.
  • Stage IV: The cancer has spread further to distant organs such as the liver or the chest.

Symptoms

Knowing the symptoms can help to obtain an earlier diagnosis. If you notice any of the following symptoms that are persistent and unusual talk to your GP in the first instance. Symptoms may include one or more of the following:

  • Abdominal bloating
  • Feeling full quickly after eating a small amount
  • Unexplained weight loss
  • Discomfort or pain in the pelvis
  • Changes in bowel habits
  • Frequent urination

Being diagnosed with an aggressive cancer can be a distressing process—speaking to a gynaecological oncologist will help you to be informed on how to effectively treat the disease.

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