Cancer of the ovaries, fallopian tubes, and peritoneum (lining of the abdomen) are closely related and are often grouped under the umbrella term of “ovarian cancer.” There are several subtypes of ovarian, fallopian tube, and primary peritoneal cancers. Low-grade serous carcinoma (LGSC) is a rare subtype that may lead to a better outlook than some other more common types of ovarian cancer.

Although most cases of ovarian cancer are found in older adults, LGSC tends to affect younger women. People are diagnosed with this type of cancer at an average age of 43. About 6 percent to 8 percent of all ovarian cancers are LGSC.

What Is Low-Grade Serous Carcinoma?

There are three main types of ovarian cancer:

• Epithelial ovarian cancers grow from the epithelial cells found on the surface of the ovary.
• Germ cell tumors develop from the cells in the ovary that make egg cells.
• Stromal cell tumors grow from the connective tissue that makes reproductive hormones.

Most ovarian cancers are epithelial tumors. These cancers can be further classified into subtypes. The most common subtype of epithelial cancer is serous cell carcinoma. Most serous tumors are high grade — they look very abnormal and grow and spread quickly. The rest are low grade. LGSC cells look similar to normal cells and don’t grow as fast.

Causes of Low-Grade Serous Carcinoma

LGSC is closely related to another type of tumor called borderline ovarian tumors (BOTs) or tumors of low malignant potential (LMP). These types of tumors are somewhere between benign (non-cancerous) and malignant (cancerous). BOTs contain cells that grow abnormally but rarely spread into nearby or distant tissues.

In rare cases, BOTs can turn into more serious cancers. LGSC usually grows from these tumors.

Gene Changes in LGSC

Ovarian cancer develops when gene changes cause a cell to start behaving abnormally. Some cancer-causing gene changes are inherited (passed down from parent to child). More often, they are acquired — they develop throughout a person’s life. All of these gene changes make cells start growing out of control.

Inherited changes in the BRCA1 or BRCA2 genes can increase a person’s risk of ovarian cancer. However, BRCA mutations almost always lead to another type of ovarian cancer, high-grade serous carcinoma. They don’t usually cause LGSC.

Other acquired gene mutations are more common in people with LGSC. These include changes in the KRAS or BRAF genes.

Risk Factors

Some lifestyle factors escalate the risk of gene changes that may lead to ovarian cancer. For example, using hormone replacement therapy during menopause increases the chances that a person will be diagnosed with serous ovarian cancer. Other ovarian cancer risk factors include older age, obesity, or a family history of ovarian cancer.

Some studies have also found that using in vitro fertilization may make a person more likely to develop borderline tumors. These may eventually grow into LGSC.

LGSC Symptoms

LGSC symptoms are similar to those seen in other more common types of ovarian cancer. Women with LGSC may notice:

• Abdominal pain
• Abdominal bloating
• Pelvic pain
• Feeling full after eating a small amount
• Needing to urinate urgently or more often than usual

These symptoms can also be caused by other conditions besides cancer. If you think that you may have any of these ovarian cancer symptoms, talk to your doctor.

Diagnosing Low-Grade Serous Carcinoma

Diagnosing ovarian cancer usually starts with a pelvic exam, in which a doctor checks to see whether they can feel anything unusual, such as a mass. During this time, the doctor may also ask about symptoms and medical history.

After an exam, the doctor may recommend certain tests. They may have a person undergo imaging tests to get a better picture of the inside of the pelvis or abdomen. These tests may include an ultrasound, computed tomography scan, or magnetic resonance imaging. These tests can detect a mass but can’t pinpoint whether the mass is cancerous.

Doctors may also recommend blood tests to measure levels of CA-125, a protein made by ovarian cancer cells. People with ovarian cancer often have high CA-125 levels. However, other non-cancerous conditions can also cause CA-125 levels to rise.

If the doctor finds a mass or another unusual feature, they may recommend monitoring it over time to see if it grows. Doctors may also suggest having surgery to remove it. During surgery, the doctor can further examine a mass and determine whether it contains cancer cells.

Staging LGSC

A cancer’s stage describes how far it has spread. Doctors usually stage ovarian cancer during surgery. The stage is reported as a number between 1 and 4, sometimes represented as Roman numbers (I through IV):

• Stage 1 — Ovarian cancer is found in one or both ovaries.
• Stage 2 — Ovarian cancer cells have spread from the ovary to the fallopian tube, or from the fallopian tube to the ovary. Or, ovarian cancer cells are found in the uterus or other nearby tissues in the pelvis.
• Stage 3 — Cancer cells are found in the lymph nodes or tissues within the abdomen.
• Stage 4 — The ovarian cancer is metastatic (it has spread to more distant locations outside the pelvis or abdomen).

LGSC has usually reached an advanced stage by the time it is diagnosed.

Treatments for Low-Grade Serous Carcinoma

Different people with LGSC may use different ovarian cancer therapies. The treatments that a doctor recommends are based on a person’s age, overall health, ovarian cancer stage, and whether the person wants children in the future.

Surgery is often the primary treatment. It is used to stage cancer and remove tumors. Once the doctor sees how far cancer has spread, they can determine how much tissue needs to be removed:

• Very early-stage LGSC that only occurs in one set of ovaries or fallopian tubes — Only the affected organs may need to be removed. Having children in the future may be an option if the other ovary and fallopian tube are left in place.
• LGSC located only within the reproductive organs — A person will likely need a bilateral salpingo-oophorectomy (removal of both ovaries and fallopian tubes) and a hysterectomy (removal of the uterus). In this case, future pregnancy will not be possible.
• Advanced ovarian cancer that has spread to other areas — A person will need to undergo debulking or cytoreductive surgery, in which the doctor removes as much cancer as possible. This may include removing parts of other tissues or organs.

Most ovarian cancers are treated with chemotherapy drugs. However, LGSC is often resistant to chemotherapy — these drugs may not work well to kill cancer cells. In particular, LGSC cells may be chemoresistant to platinum-based drugs such as Paraplatin (carboplatin). However, chemotherapy is effective for some people with LGSC, so it is usually recommended as a starting treatment.

Another LGSC treatment option may be targeted therapy drugs. These medications attack specific molecules found in cancer cells. Targeted therapies like Avastin (bevacizumab) may be given along with chemotherapy. Researchers are also using clinical trials to study other types of targeted therapy drugs in LGSC.

Hormone therapy may also help treat LGSC. These cells often contain hormone receptor proteins called estrogen receptors and progesterone receptors. These proteins allow the cancer cells to divide and make new cells. In these types of cancers, hormone therapies can decrease signals that tell the cancer cells to grow. Hormone therapy drugs, including Nolvadex (tamoxifen) or the aromatase inhibitors Arimidex (anastrozole) and Femara (letrozole), may be given once chemotherapy is complete.

LGSC Outlook

Low-grade serous ovarian cancer grows more slowly than high-grade subtypes, so people with LGSC may have a slightly better prognosis (outlook).

One study found that people with LGSC live for an average of 7.6 years after being diagnosed. In this study, women who did not receive chemotherapy had a better outlook than women who took chemotherapy drugs. Additionally, women with advanced-stage LGSC had much better outcomes when lymph nodes near the cancer were surgically removed:

• Women who had their lymph nodes taken out lived an average of 8.9 years.
• Women who still had their lymph nodes after surgery lived an average of 4.8 years.

Other prognostic factors may affect a person’s likelihood of having a good outlook. The lower the cancer stage is, the better the prognosis will be. Additionally, having no residual disease (no visible cancer) after surgery leads to better outcomes.

If you are interested in learning more about 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 3,000 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 low-grade serous carcinoma? Share your experiences in the comments below, or start a conversation by posting on your Activities page.