What is Ovarian Cancer?

Ovarian cancer is cancer that begins in the cells that make up the ovaries. Cancer that originates at another site (e.g., breast or colon) and spreads to the ovaries is not considered ovarian cancer.

Diagram of uterus and ovaries.

There are many types of tumors that can start in the ovaries. Ovarian cysts are examples of other growths that can occur on the ovaries. Most ovarian cysts are not cancerous. They are fluid-filled sacs that form on the surface of the ovary. Cysts usually go away without treatment, but a doctor may recommend removal, especially if it seems to be growing, to ensure that they do not become cancerous.

 

Types of Ovarian Cancer

There are several different types of ovarian cancer, which are classified according to the type of cell from which they start.

 

Epithelial ovarian carcinoma (EOC):

This is the most common type of ovarian cancer, which arises from the cells covering the surface of the ovaries (epithelial cells). This type accounts for 65-90 percent of ovarian cancer cases.

Epithelial ovarian carcinomas include the following types:

Percent of EOC cases
Serous 40%
Endometriod 20%
Mucinous 1%>
Clear Cell 6%
Undifferentiated 15%
Borderline tumors 15%

 

Epithelial carcinomas are further divided into grades according to how the degree of differentiation, or maturity, of the cells making up the tumor.

Grade 0: tumors of low malignant potential, also known as borderline tumors, are the most well-differentianted
Grade 1: well-differentiated
Grade 2: moderately differentiated
Grade 3: poorly differentiated

Well-differentiated tumors have a better prognosis than poorly differentiated tumors. Clear cell and undifferentiated carcinoma have a poorer prognosis than the other cell types.

 

Germ cell carcinoma:

This type of ovarian cancer arises from the cells that form the eggs and makes up about 5 percent of ovarian cancer cases. While germ cell carcinoma can occur in women of any age, tends to be found most often in women in their earlier 20s. There are six main types of germ cell carcinoma, but the three most common types are:

  • Teratomas
  • Dysgerminomas
  • Endodermal sinus tumors

There are also many tumors that arise in the germ cells that are benign.


Stromal carcinoma:

Ovarian stromal carcinoma accounts for the remaining 5 percent of ovarian cancer cases. It develops in the connective tissue cells that hold the ovary together and those that produce the female hormones (estrogen and progesterone). The two most common types are:

  • Granulosa cell tumors
  • Sertoli-Leydig cell tumors

Unlike with epithelial ovarian carcinoma, 70 percent of the cases of stromal carcinoma are diagnosed in Stage I.

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Staging

Ovarian cancer is staged at surgery. Staging is based on classifications devised by FIGO (International Federation of Gynecology and Obstetrics - http://www.figo.org.

Stage I - Cancer is limited to one or both ovaries.

IA - Cancer is limited to one ovary and the tumor is confined to the inside of the ovary. (There is no cancer on the outer surface of the ovary.) There is no ascites present containing malignant cells. The surface of the tumor is unruptured.

IB - Cancer is limited to both ovaries without any tumor on their outer surfaces. There is no ascites present containing malignant cells. The surface of the tumor is unruptured.

IC - The tumor is classified as either Stage 1A or 1B and one or more of the following are present: (1) tumor is present on the outer surface of one or both ovaries; (2) at least one of the tumors has ruptured; and (3) there is ascites present or abdominal (peritoneal) washings containing malignant cells.

Stage II - The tumor involves one or both ovaries with extension to other pelvic structures.

IIA - The cancer has extended to and/or involves the uterus or the fallopian tubes or both.

IIB - The cancer has extended to the bladder or rectum.

IIC - The tumor is classified as either Stage IIA or IIB and one or more of the following are present: (1) tumor is present on the outer surface of one or both ovaries; (2) at least one of the tumors has ruptured; and (3) there is ascites containing malignant cells or with abdominal (peritoneal) washings containing malignant cells.

Stage III - The tumor involves one or both ovaries, and one or both of the following are present: (1) the cancer has spread beyond the pelvis to the lining of the abdomen; and (2) the cancer has spread to the lymph nodes. The tumor is limited to the true pelvis but with histologically-proven malignant extension to the small bowel or omentum.

IIIA - During the staging operation, the practitioner can see cancer involving one or both of the ovaries, but no cancer is grossly visible in the abdomen and it has no spread to the lymph nodes. However, when biopsies are checked under a microscope, very small deposits of cancer are found in the abdominal (peritoneal) surfaces.

IIIB - The tumor is in one or both ovaries, and deposits of cancer are present in the abdomen that are large enough for the surgeon to see but not exceeding 2 cm in diameter. The cancer has not spread to the lymph nodes.

IIIC - The tumor is in one or both ovaries, and one or both of the following is present: (1) the cancer has spread to lymph nodes; (2) the deposits of cancer exceed 2 cm in diameter and are found in the abdomen.

Stage IV - Growth of the cancer involves one or both ovaries and distant metastases to the liver or lungs have occurred. Finding ovarian cancer cells in the excess fluid accumulated around the lungs (pleural fluid) is also evidence of stage IV disease.

The stage of ovarian cancer at diagnosis is also the most important indicator of prognosis (prediction of duration, course and outcome of the disease)


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Sources

  1. New Directions in Ovarian Cancer Research from Report of Strategic Planning Conference December 8-9, 1997, Sponsored by National Cancer Institute, Society of Gynecologic Oncologists, and PHS Office of Women's Health
  2. NCI, What You Need to Know About...Ovarian Cancer. NIH Publication No. 00-1561
  3. Everyone's Guide to Cancer Therapy: How Cancer Is Diagnosed, Treated and Managed Day to Day. 3rd ed. Malin Dollinger, M.D., Ernest H. Rosenbaum, M.D., Greg Cable et al.
  4. Myths & Facts About Ovarian Cancer: What you need to know. M. Steven Piver, MD, Gamal Eltabbakh, MD


This information has been taken with permission from the Ovarian Cancer National Alliance, http://ovariancancer.org.
 

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