High-grade serous carcinoma (HGSC) is the most common type of ovarian cancer. It develops when cells in the ovaries, fallopian tubes, or peritoneum (lining of the abdomen) grow in an out-of-control manner.

Originally, doctors thought that ovarian cancer and fallopian tube cancer were two related but different cancers. Recently, however, researchers have discovered that many cases of HGSC begin growing in the fallopian tubes and later spread to the ovaries or peritoneum. Because of this, scientists usually group ovarian cancer, fallopian tube cancer, and primary peritoneal cancers together.

What Is High-Grade Serous Carcinoma?

Doctors classify ovarian cancers based on the cell type a person’s tumor came from. The three main types of ovarian cancer are:

• Epithelial
• Germ cell
• Stromal

About 9 out of 10 cases of ovarian cancer are epithelial ovarian tumors. They develop in the epithelial cells found on the outer surface of the ovaries and fallopian tubes. Epithelial ovarian cancer is further divided into subtypes, the most common being serous cell carcinoma.

Doctors assign cases of ovarian cancer a grade based on how abnormal a person’s cells look and how fast those abnormal cells are growing. Serous cell carcinomas can be early-grade — cancer cells that look similar to normal ovarian cells. And they can be later-grade — cancer cells that look very abnormal and are rapidly growing in a disorderly way. Later-grade serous ovarian carcinoma can spread quickly and often leads to a poor prognosis (outlook). About 3 out of 4 people with ovarian cancer have HGSC.

High-Grade Serous Carcinoma: Causes and Risk Factors

Cancer develops when genes undergo changes. Genes tell cells what their jobs are and how to do them. Gene changes can cause cells to create abnormal proteins that force cells to grow too quickly, allow them to ignore signals that normally slow down growth, or make it difficult for cells to repair damage.

With HGSC, cells often have certain types of gene changes. In fact, 19 out of 20 people with this cancer have changes in a gene called TP53.

About 1 out of 4 people with HGSC have changes in their BRCA1 or BRCA2 genes. Such BRCA gene mutations cause additional damage to build up within cells. In general, BRCA mutations are usually passed down within families. Those who are born with changes in these genes are more likely to be diagnosed with both ovarian and breast cancers.

High-Grade Serous Carcinoma Risk Factors

Most cases of ovarian cancer are not caused by inherited gene changes. They usually develop over the course of a person’s life. Certain environmental or lifestyle factors can increase the chances of these gene changes occurring, raising a person’s risk of cancer.

In general, ovarian cancer risk factors include:

• Older age
• Obesity
• Hormone replacement therapy (HRT) use after menopause

Researchers have also found that people with pelvic inflammatory disease are more likely to develop the HGSC subtype. Additionally, people who have had breast cancer are 3 times more likely to develop HGSC.

On the other hand, giving birth, breastfeeding, and using oral contraceptives (birth control pills) can each reduce a person’s risk of ovarian cancer.

Symptoms of High-Grade Serous Carcinoma

The symptoms of HGSC often don’t appear until cancer has grown and begun to spread.

People with symptoms may notice:

• Pain in the abdomen or pelvis
• Abdominal bloating
• Feeling full very quickly
• Loss of appetite
• Needing to urinate often
• Urinary urgency (suddenly feeling like you need to urinate right away)

If you notice any of these potential symptoms of ovarian cancer, talk to your doctor. Often, they are caused by noncancerous conditions, but it is important to get any symptom checked out.

Diagnosing High-Grade Serous Carcinoma

If your doctor suspects that you may have ovarian cancer, they may use several different tests to help them make a diagnosis.

Those tests may include:

• A pelvic exam — Examining reproductive organs for anomalies and changes that may signal ovarian cancer
• Imaging tests — Using an image of the inside of a person’s body — such as an ultrasound, CT, or MRI scan — to check for abnormal growths
• Blood tests — Sampling and screening a person’s blood to check for cells that indicate ovarian cancer is in their body
• Surgery — Removing a mass to determine if it is cancerous
• Biopsy — Removing tissue or a mass from a person’s body to send pieces of it to a lab for further examination

In the laboratory, pathologists (doctors who specialize in studying tissues) analyze biopsy samples. Then they determine whether cells are cancerous and, if so, the type of ovarian cancer they represent. This is possible with high-grade serous ovarian cancer cells as they have a distinct appearance under a microscope. They also contain certain proteins not found in other types of ovarian cancer.

As for blood tests, a doctor may check the levels of the protein CA-125 in a person’s blood. Levels of this protein are often high in people with ovarian cancer.

High-Grade Serous Carcinoma Stages

When diagnosing ovarian cancer, doctors will assign a stage number using a staging system called FIGO (so-called as it’s based on the guidelines set by the International Federation of Gynecology and Obstetrics). This number describes how advanced the cancer is and how far it has spread in a person’s body. (Sometimes stages are referred to by Roman numerals. e.g., stage IV instead of stage 4.)

The FIGO stages for ovarian cancer are:

• Stage 1 — Cancer is found in the ovaries (one or both) or fallopian tubes, but it has not spread to other tissues.
• Stage 2 — Cancer has started in the ovaries (one or both) and spread to the fallopian tubes, or vice versa. Alternatively, cancer has spread from the ovaries or fallopian tubes to other nearby tissues in the pelvis, such as those of the uterus.
• Stage 3 — Cancer has spread from the pelvis to lymph nodes or tissues in the abdomen.
• Stage 4 — Cancer has spread to the spleen, liver, or tissues outside of the pelvis and abdomen.

About 7 out of 10 cases of HGSC are at an advanced stage (stage 3 or stage 4) by the time they are diagnosed.

High-Grade Serous Carcinoma Treatments

Doctors typically recommend a combination of treatment types, including surgery, chemotherapy, or targeted therapy. The treatments you receive may depend on your age, overall health, cancer stage, and whether you want to have children in the future.

Treatment for HGSC usually begins with surgery. During this procedure, a surgeon will try to remove as much cancer as possible. For early-stage tumors, this may involve removing a single ovary that contains a mass. For later-stage disease, surgery often includes removing multiple tumors and possibly parts of different organs or tissues that contain cancer. Doctors also can determine the stage of a person’s cancer during surgery. (Surgery itself may be called debulking surgery or cytoreductive surgery.)

Most people with HGSC receive chemotherapy drugs. These often include platinum-based drugs like Paraplatin (carboplatin) and Platinol (cisplatin), in addition to others like Taxol (paclitaxel) or Taxotere (docetaxel). People usually undergo at least six rounds of chemotherapy after surgery. In some cases, several rounds of chemotherapy may be given before surgery in an effort to shrink tumors before removing them. This is called neoadjuvant chemotherapy.

Targeted therapies may also be an option for cases of ovarian cancer that contain specific gene changes. Targeted therapy drugs may include Avastin (bevacizumab) — or poly (ADP-ribose) polymerase (PARP) inhibitors such as Lynparza (olaparib), Rubraca (rucaparib), and Zejula (niraparib).

If a person’s cancer goes away after initial treatments, they will still need regular follow-up visits with their health care team to look for signs that the cancer has relapsed (come back). These visits are critical, because most cases of HGSC eventually return. Relapsed cancer may be treated with a different chemotherapy regimen.

Clinical trials may also be an option for people with any stage of ovarian cancer. During a clinical trial, participants may be able to access new medications or treatment plans.

Prognosis for High-Grade Serous Carcinoma

Because HGSC is usually not discovered until after it has begun to spread, it can be especially hard to treat. Overall, people with this type of ovarian cancer live an average of 3.4 years after being diagnosed. However, a person’s exact prognosis (medical forecast) depends on several other factors.

Your cancer stage is one such factor. People with early-stage ovarian cancer are more likely to live longer than those with advanced ovarian cancer.

Researchers have calculated survival rates across all subtypes of epithelial ovarian cancer:

• When cancer is located solely in the ovary or fallopian tubes, a person is 93 percent as likely to live for 5 years or more.
• When cancer has spread to nearby tissues, a person is 75 percent as likely to live for 5 years or more.
• When cancer is metastatic (has spread to distant organs or tissues), a person is 31 percent as likely to live at least 5 years.

Other factors also affect a person’s prognosis. People with HGSC who are less than 65 years old are more likely to live longer compared with those who are older. Those who are in better overall health, are not obese, or have less ascites (fluid in the abdomen) may also have a better outlook. If you’d like to know more about how your own characteristics affect your prognosis, talk to your health care team.

Talk With Others Who Understand

On MyOvarianCancerTeam, the social network for people with ovarian cancer and their loved ones, more than 3,500 members come together to ask questions, give advice, and share their stories with others who understand life with ovarian cancer.

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