Ovarian clear cell carcinoma (OCCC) is a rare type of ovarian cancer. It was named due to its appearance — when examined under a microscope, cells from clear cell tumors look transparent. Clear cell cancers can also occur in other organs within the reproductive system.

There are three main types of ovarian cancer: epithelial tumors, stromal tumors, and germ cell tumors. OCCC is a rare subtype of epithelial cancer. In the United States, OCCC affects women of different racial backgrounds at different rates:

• OCCC makes up 11.1 percent of epithelial ovarian cancers seen in Asian women.
• OCCC accounts for 4.8 percent of epithelial ovarian cancers diagnosed in white women.
• OCCC makes up 3.1 percent of epithelial ovarian cancers diagnosed in Black women.

Other more common types of ovarian cancer, such as high-grade serous carcinoma, are more common in older women. However, OCCC tends to be diagnosed at a younger age. The average age at diagnosis is 55.

Clear Cell Carcinoma Causes and Risk Factors

Cancer is caused by gene changes that affect the way a cell grows. Genes tell cells how to make proteins, which carry out many tasks that keep the cells functioning properly. When genes develop mutations, cells may produce too much of a protein, not make enough protein, or create abnormal versions of a protein. These changes may turn a cell cancerous, making a cell look and behave abnormally.

OCCC cells often contain mutations in genes like ARID1A, PIK3CA, and PTEN. These gene changes make cells begin growing more quickly than they should, producing many new cancer cells that form tumors. OCCC cells also have changes in genes that are responsible for healing damage. This means that additional gene mutations continue to build up in these cells.

Endometriosis and Clear Cell Carcinoma

The main risk factor for clear cell ovarian cancer is endometriosis. In this condition, the tissue that is similar to tissue from the uterus begins growing outside of the uterus. About half of people with OCCC have endometriosis.

Experts don’t yet fully understand the link between endometriosis and ovarian cancer. However, researchers have found that some areas of uterine tissue may begin developing cancer-causing gene mutations. This abnormal tissue may eventually become cancerous and turn into OCCC.

Symptoms of Clear Cell Carcinoma

Like other types of ovarian tumors, clear cell carcinoma of the ovary can lead to the following symptoms:

• Abdominal bloating or swelling
• Abdominal pain
• Pelvic pain
• Back pain
• Loss of appetite
• Needing to urinate more often than usual
• Tiredness
• Nausea or indigestion
• Changes in the menstrual period

Women with OCCC are at risk for experiencing problems with blood clots. This type of ovarian cancer may lead to deep vein thrombosis (a blood clot that develops in a vein in the leg or arm) or a pulmonary embolism (blockage of a blood vessel within the lungs).

If you think you are experiencing symptoms of ovarian cancer, notify your health care team.

Diagnosing Clear Cell Carcinoma

When diagnosing OCCC, your doctor may use multiple types of tests, including:

• A pelvic exam — Your doctor will ask about your symptoms and medical history and look for signs of cancer such as a pelvic mass or growth.
• Blood tests — High levels of the CA-125 protein in your blood may be a sign of ovarian cancer.
• Imaging tests — To look inside your body, your doctor may recommend an ultrasound, computed tomography, or magnetic resonance imaging.

If your doctor finds a mass or lesion (area of tissue damage), you may not need immediate treatment. Masses may be monitored over time through regular follow-up visits with your health care team.

In other cases, you may need surgery to remove a mass. During surgery, your doctor can further examine your cells to determine whether they are cancerous. They may take a biopsy (sample of tissue) and send it to a lab so it can be studied under a microscope. By examining the appearance of the cells and looking for particular proteins, your health care team can determine whether cells are cancerous and find out what type of ovarian cancer they are.

Clear Cell Carcinoma Stages

Your doctor can also determine the cancer stage during surgery. The stage describes whether cancer has begun to spread. Doctors use a system called FIGO to classify ovarian cancer into four stages. Cancer stages are sometimes represented with Roman numerals, as stages I through IV. FIGO stage 1 (stage I) is the least advanced and stage 4 (stage IV) is the most advanced:

• Stage 1 — Cancer cells are located in one or both ovaries or fallopian tubes.
• Stage 2 — Cancer cells have spread to nearby tissues in the pelvis such as the uterus.
• Stage 3 — Cancer cells are found in the lymph nodes or tissues in the abdomen.
• Stage 4 — Cancer cells have spread outside of the pelvis and abdomen.

OCCC is more likely to be diagnosed at an early stage compared with other types of ovarian cancer. Between 57 percent and 81 percent of OCCC cases are discovered when they are stage 1 or stage 2.

Treatments for Clear Cell Carcinoma

OCCC is treated similarly to other types of epithelial ovarian carcinoma. Your exact treatment plan may depend on factors like your age, overall health, cancer stage, and whether you want children in the future.

Ovarian cancer treatment typically starts with surgery. This may include:

• Bilateral salpingo-oophorectomy — Removal of the ovaries and fallopian tubes
• Hysterectomy — Removal of the uterus
• Lymphadenectomy — Removal of the lymph nodes
• Omentectomy — Removal of the layer of fat that covers the abdominal organs
• Cytoreductive or debulking surgery — Removal of as much cancer as possible, which may include cutting out parts of different tissues or organs

If doctors remove both ovaries or the uterus, you will not be able to get pregnant. Some people with very early-stage ovarian cancer may only need one ovary and fallopian tube removed, which maintains fertility. However, this is usually not an option for people with OCCC.

Ovarian cancer is usually treated with platinum-based chemotherapy drugs like Paraplatin (carboplatin) or Platinol (cisplatin). However, OCCC tends to be resistant to these drugs, so they may not work as well. Most women with OCCC still undergo chemotherapy because this treatment can be effective for some people. However, chemotherapy may not be necessary for people with stage 1 OCCC.

Targeted therapies are drugs that recognize and attack specific proteins found on cancer cells. Several targeted therapies have been developed to help treat other types of ovarian cancer. However, OCCC cells tend to contain different proteins. These medications may not work as well for this subtype. However, doctors may recommend taking Avastin (bevacizumab) along with chemotherapy. Additionally, researchers are currently conducting clinical trials to look for additional targeted therapy drugs that may help people with OCCC.

Clear Cell Carcinoma Prognosis

A person’s prognosis (outlook) is affected by many factors. One of the biggest factors is the cancer stage. Those who have advanced-stage disease tend to have worse survival rates than those with early-stage disease:

• About 84.6 percent of people with stage 1 OCCC live for five years or more after being diagnosed.
• Around 66.1 percent of people with stage 2 disease live at least five years.
• About 31.5 percent of those with stage 3 disease live five years or more.
• About 12.5 percent with stage 4 disease live at least five years.

Other prognostic factors can also determine a person’s outcome. Women with endometriosis are more likely to have a good prognosis. Factors that may lead to a poor prognosis include:

• Older age
• High blood levels of CA19-9 or HE4, molecules made by cancer cells
• Increased amounts of ascites (fluid in the abdomen)
• Lymph node metastasis (cancer cells spreading to nearby lymph nodes)
• Changes in the ARID1A gene

If you would like to know more about how your risk factors affect your prognosis, talk to your health care team.

Talk With Others Who Understand

MyOvarianCancerTeam is the social network for people with ovarian cancer. On MyOvarianCancerTeam, more than 8,900 members come together to ask questions, give advice, and share their stories with others who understand life with ovarian cancer.

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