High-grade serous carcinoma (HGSC) is the most common type of ovarian cancer. It develops when cells in the ovaries, fallopian tubes, or peritoneum (the inside 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. Researchers have since 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

Nearly 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. Epithelial ovarian cancer is further divided into subtypes. The most common is high-grade serous cell carcinoma.

Doctors assign cases of ovarian cancer a grade based on how abnormal the tumor cells look. Serous cell carcinomas can be early-grade — cancer cells that look closely 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 lead to a poor prognosis (outlook). About 3 out of 4 people with ovarian cancer have HGSC.

High-Grade Serous Ovarian 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. This may allow them to ignore signals that normally slow 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.

One small study showed that 1 out of 4 people with HGSC had 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 have a higher risk for ovarian cancer, breast cancer, or both.

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 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 three 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
• Loss of appetite or quickly feeling full
• Frequent urination
• Urinary urgency (feeling the need to urinate right away)
• Low back pain

If you notice any of these potential symptoms of ovarian cancer, talk to your doctor. Often, the cause isn’t cancer, but it’s important to get any symptom checked out.

Diagnosing High-Grade Serous Carcinoma

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

Those tests may include:

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

In the laboratory, pathologists (doctors who specialize in studying tissues under a microscope) analyze biopsy samples. 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 cancer antigen 125 (CA-125) in your blood. Levels of CA-125 may be higher 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, which is named for 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 III or stage IV instead of stage 3 or 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 organs.
• 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 organs in the pelvis, such as those of the uterus.
• Stage 3 — Cancer has spread from the pelvis to lymph nodes or tissues elsewhere in the abdomen, but not to distant sites.
• Stage 4 — Cancer has spread to the spleen, liver, lungs, or other 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’re diagnosed.

High-Grade Serous Carcinoma Treatments

Doctors typically recommend a combination of ovarian cancer treatments, including surgery, chemotherapy, or targeted therapy. Others may also need radiotherapy or immunotherapy. The treatments you receive may depend on several factors, including the cancer stage and genetic features of the tumor.

Surgery

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 cancer during surgery. (Surgery itself may be called debulking surgery or cytoreductive surgery.)

Chemotherapy

Most people with HGSC receive chemotherapy drugs. These often include platinum-based drugs like carboplatin and cisplatin, in addition to others like paclitaxel or docetaxel.

The amount of chemotherapy recommended after surgery depends on the stage of the cancer. 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 Therapy

Targeted therapies may also be an option for cases of ovarian cancer that contain specific gene changes. Targeted therapy drugs may include angiogenesis inhibitors such as bevacizumab or poly (ADP-ribose) polymerase (PARP) inhibitors such as olaparib and rucaparib. Antibody drug conjugates are another category of targeted therapy your doctor may recommend.

Treating Relapsed HGSC

If your cancer goes away after initial treatments, you’ll still need regular follow-up visits with your healthcare team to look for signs that the ovarian cancer has relapsed (come back). These visits are critical, because most cases of HGSC eventually return. HGSC most often recurs within three years, and cancers with a later stage or grade have a greater chance of relapse. Relapsed cancer may be treated with a different chemotherapy regimen. In some cases, it can also be treated with repeat surgery, another targeted therapy, radiotherapy, or immunotherapy.

Clinical Trials

Clinical trials may 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 3.3 years after being diagnosed. However, a person’s overall survival 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 stages of invasive epithelial ovarian cancer. These five-year relative survival rates share the likelihood of someone living with this cancer type and stage for five years or more, compared to someone without that cancer type.

• When cancer is located solely in the ovary or fallopian tubes, the five-year relative survival rate is 93 percent.
• When cancer has spread to nearby tissues, the five-year relative survival rate is 75 percent.
• When cancer is metastatic (has spread to distant organs or tissues), the five-year relative survival rate is 31 percent.

Other factors also affect a person’s prognosis. For instance, people with HGSC who are younger than 65 years old are more likely to live longer compared with those who are older. If you’d like to know more about how your own characteristics affect your prognosis, talk to your oncologist or another healthcare provider.

Talk With Others Who Understand

On MyOvarianCancerTeam, the social network for people with ovarian cancer and their loved ones, more than 7,000 members come together to ask questions, give advice, and share their stories with others who understand life with ovarian cancer.

Have you been diagnosed with high-grade serous carcinoma? Share your experiences in the comments below, or start a conversation by posting on your Activities page.