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clear cell ovarian cancer

Clear cell ovarian cancer is the second to third most common type of ovarian cancer. It accounts for 5 to 10% of ovarian cancers and is more common in Eastern Asia. The median age of women with clear cell carcinoma is 55 years old.

It is called ‘clear cell’ because of how the cancer looks under the microscope. The cells in the tumour look clear, like bubbles


The symptoms of clear cell ovarian cancer are similar to those of other ovarian cancers and may include any of the following: bloating; eating less and feeling fuller; bowel habit changes; needing to pee more or urgently; or abdominal, pelvic or back pain. In addition, thromboembolic complications, such as deep venous thrombosis and pulmonary embolism are more common with clear cell carcinoma compared to other ovarian cancers. As with all ovarian cancers, symptoms that last for four weeks or longer, particularly if they are unusual, frequent or worsening, should be investigated.

Diagnosis of clear cell ovarian cancer

Clear cell ovarian cancer is an epithelial cancer. Epithelial tissues are widespread throughout the body and form the covering of all body surfaces (like the outer surface of our skin and eyes), line body cavities and hollow organs – they are the major tissue in glands. ⁠

Clear cell carcinoma is frequently associated with endometriosis, clear cell adenofibroma and clear cell atypical proliferative (borderline) tumours. Investigations for ovarian cancer usually include a pelvic examination, CA-125 blood test and imaging like a transvaginal ultrasound or CT.

To confirm the diagnosis, a sample of the tumour is examined under a microscope by a specialist doctor called a pathologist.

Clear cell carcinoma tends to be diagnosed at an earlier stage than other ovarian cancers.

Genetic risk factors

Clear cell ovarian cancer is associated with Lynch Syndrome, a rare inherited condition caused by an abnormality in one of four mismatch repair genes (MLH1, MSH2, MSH6, and PMS2). It can increase the risk of a variety of cancers including colorectal, endometrial (uterine), stomach, ovarian, small intestine, kidney, brain or liver cancer.

A genetic blood test can identify whether someone is a carrier for a Lynch Syndrome mutation.

BRCA mutations may occur in clear cell ovarian cancer, but at a lower frequency than in high-grade serous ovarian cancer.

Treatments for clear cell ovarian cancer

In New Zealand, treatment decisions are made in a multi-disciplinary meeting. Doctors present individual cases to a group of specialists that includes gynae-oncologists, oncologists, pathologists and radiologists and collectively they decide what treatment should be offered.

Initial treatment usually consists of surgery and/or chemotherapy. Chemotherapy may be administered through the veins (intravenous) or directly into the abdomen (intraperitoneal). Most people receive some form of carboplatin/paclitaxel chemotherapy. You can read more about the treatments for clear cell carcinoma in the NCCN Ovarian Cancer Guidelines. The NCCN guidelines are an American resource and some treatments may differ in New Zealand.

Recurrence of clear cell ovarian cancer

If the cancer comes back surgery and/or chemotherapy may be an option. Possible chemotherapy treatments include platinum-based regimens such as carboplatin and non platinum-based chemotherapies such as paclitaxel, gemcitabine, doxorubicin and topotecan.

Recurrent clear cell tumours are relatively resistant to chemotherapy.

Unfunded treatments

Some ovarian cancer treatments available overseas are not funded in New Zealand, or may have additional restrictions as to their use. These include anti-vascular endothelial growth factor (VEGF) agents like bevacizumab (avastin); and chemotherapy agents like pegylated liposomal doxorubicin hydrochloride (caelyx). People can ask their doctor if any unfunded treatments that could help them are available, however unfunded treatments can only be prescribed in the private healthcare system.

Some life insurance policies and health insurance may pay a lump sum following a cancer diagnosis, to help pay for unfunded treatments. Other people might decide to fundraise to cover the cost of their treatments.

Not everyone will benefit from an unfunded treatment.

Clinical trials

A clinical trial is research involving human participants. Clinical trials can offer new or different treatment options for people with ovarian cancer and help doctors make better decisions for people in the future. Medications in a clinical trial are provided at no cost to participants.

There may be unknown benefits and unique risks to participating in a clinical trial. An oncologist or gynae-oncologist can advise if there are any clinical trials which people may be eligible for.

Agents currently being investigated overseas for clear cell carcinoma include treatments targeting blood vessel growth (bevacizumab, sunitinib, nintendanib) and immune checkpoint inhibitors (nivolumab, durvalumab).

As of December 2023, there is one clear cell ovarian cancer specific clinical trial in New Zealand called Combination Immunotherapy in Rare Cancers Under InvesTigation (MOST-CIRCUIT) in Auckland. If you are interested in participating in a clinical trial, speak to your oncologist. They will be able to advise you if there are any additional ovarian and general clinical trials available.

Find out more information about ovarian cancer.

Note: this content has been reviewed by a gynaecological cancer specialist in New Zealand. Information is provided for general use and should not be a substitute for professional medical advice.

Last reviewed: 16 January 2024