Ovarian cancer (ovarian carcinoma) occurs when cells in the ovary become mutated and begin growing out of control. Because there are different types of cells that make up the ovary, there are many subtypes of ovarian cancer. Most cases of ovarian cancer are subtypes called epithelial ovarian cancer, which is by far the most common.

There are also many uncommon or rare subtypes of ovarian cancer. By definition, a rare condition is one that affects fewer than 200,000 people in the United States, according to the National Institutes of Health.

Overview of Ovarian Cells

There are three main types of cells that make up the ovary:

• Epithelial cells, which cover the ovary
• Germ cells (eggs), the main reproductive cells within the ovary
• Sex cord-stromal cells, which are responsible for making essential hormones and supporting the structure of the ovary

Each of these cell types can give rise to different kinds of ovarian tumors, including rare subtypes of ovarian cancer.

Epithelial Ovarian Tumors

Epithelial ovarian carcinoma is by far the most common type of ovarian tumor, representing 85 percent to 90 percent of all ovarian cancers. The vast majority of these are known as high-grade serous carcinomas. “Grade” refers to how abnormal cancer cells and tissue look when evaluated under a microscope. Usually, the more abnormal and mutated a tumor is, the faster it grows and spreads.

The majority of ovarian cancers today are discovered late and are high-grade. This is because symptoms are usually vague (such as bloating), especially early symptoms. In addition, no high-quality regular screening tests exist for early detection.

Risk factors that are common across epithelial tumor types are hormone therapy, weight gain, and older age. Most women diagnosed with epithelial tumors tend to be postmenopausal — usually in their late 50s, 60s, or older.

Many types of rarer epithelial ovarian tumors are lower-grade and have a better outcome. Rarer types of epithelial tumors include mucinous carcinomas, which can be low grade or high grade, and low-grade serous carcinomas. They also include endometrioid carcinomas, small cell carcinomas, and clear cell carcinomas. It’s important to understand the special characteristics of each of the rarer types of ovarian epithelial tumors.

Mucinous Carcinoma

• Most mucinous tumors of the ovary (about 80 percent) are not originally from the ovary. Approximately 45 percent originate in the digestive tract, spreading to the ovaries from the stomach, intestines, or other organs. This is sometimes called a Krukenberg tumor.
• Mucinous cancers that arise in the ovary are treated in a similar way to serous carcinomas. Chemotherapy is the mainstay for mid- and late-stage malignancies.

Endometrioid Carcinoma

• Endometrioid carcinomas are made up of cells that resemble the endometrium, or the cells that line the inside of the uterus. These are the cells that shed during menstrual cycles.
• One risk factor for endometrioid carcinoma is having endometriosis.

Clear Cell Carcinoma

• Clear cell carcinoma typically affects people who are younger, with a median age of 55 years.
• Like endometrioid carcinomas, one risk factor for clear cell tumors is having endometriosis.

Small Cell Carcinoma

• Small cell carcinoma is highly malignant. Unlike other epithelial ovarian tumors, it usually presents in young women under the age of 40.
• This type of carcinoma can be associated with elevated calcium levels in the blood (hypercalcemia). Hypercalcemia is often associated with nausea, bone pain, frequent urination, and behavioral or mental status changes.

Ovarian Tumors From Outside the Ovary

• Epithelial ovarian cancers can arise from cells right outside of the ovary, like the inner lining of the abdomen (the peritoneum) or the fallopian tubes.
• Tumors that grow from cells of the peritoneum are called primary peritoneal cancer. Along with fallopian tube cancer, they behave like epithelial ovarian tumors.
• Brenner tumors are tumors from cells resembling those found in the bladder. These masses are usually benign (not cancerous).

Sex Cord-Stromal Tumors

Sex cord-stromal tumors involve cells that produce sex hormones like estrogen, progesterone, and testosterone. Estrogen and progesterone are made in cells called granulosa cells and theca cells. Testosterone-producing cells are called Sertoli cells and Leydig cells.

Tumors from these cells are named accordingly, and they produce a large amount of their corresponding hormones. Because of the effects of these hormones, these tumors are usually recognized early and in low-grade stages.

Granulosa-Theca Cell Tumors

• Granulosa-theca cell tumors make up about 2 percent of all ovarian tumors. They occur most often in young adults.
• These tumors secrete abnormally large amounts of estrogen, causing irregular menstrual cycles in premenopausal women and abnormal bleeding in postmenopausal women.
• Surgery to completely remove the hormone-producing tumor is the most common treatment. Surgery can sometimes be followed by hormone therapy, radiation therapy, or chemotherapy as well.

Sertoli-Leydig Cell Tumors

• Sertoli-Leydig cell tumors produce testosterone, resulting in the development of masculine features, like a deeper voice or facial hair growth, in young women affected by this type of ovarian cancer.
• Treatment usually consists of surgery, plus radiation or chemotherapy if the tumor remains or if it has spread.

Germ Cell Tumors

Germ cell tumors arise when immature, newly released, or fertilized egg cells form tumors of their own. These rare cancers include dysgerminomas, teratomas, yolk sac tumors, and choriocarcinomas. Because younger women have more eggs, germ cell tumors can present at a much younger age compared to other types of ovarian tumors. The average age of someone diagnosed with a germ cell tumor is about 16 to 20 years of age, but they can occur in older women or even children.

Dysgerminoma

• Dysgerminoma is the most common cancerous germ cell tumor of the ovary. It makes up 1 percent to 2 percent of all primary ovarian tumors.
• These tumors do not secrete any hormones.
• Dysgerminoma tumors are solid and slow-growing, so they can be quite large when discovered.
• About two-thirds of these tumors are diagnosed as stage 1 — the earliest stage of cancer.

Teratoma

• Teratomas are formed when a germ cell divides into different cell types and layers, similar to the cells found in early embryos and adults.
• Teratomas can affect both men and women. There are two types: mature teratomas (which contain adult human cells or tissue) and immature teratomas (which contain embryonic cells or tissue). Most ovarian teratomas are mature, benign, and called dermoids.
• Immature teratomas are more likely to be malignant (grow and spread quickly) and have a poorer outcome for people affected.

Yolk Sac Tumors

• Yolk sac tumors are made up of embryonic cells, like those found in teratomas. Unlike teratomas, they do not have different layers of several types of cells.
• Like immature teratomas, these tend to have a poor outcome.

Choriocarcinoma

• Choriocarcinomas arise from cells that resemble those found in placentas. They can arise after having a molar pregnancy, which is when a fertilized egg does not grow into an embryo, but becomes a mass of disorganized cells.
• This type of tumor is highly malignant. It can spread quickly to other parts of the body.

Talk With Others Who Understand

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