What is ovarian cancer?

Ovarian cancer starts in the cells of the ovary. A cancerous (malignant) tumour is a group of cells that can grow into and destroy nearby tissue. It can also spread (metastasize) to other parts of the body. Cancerous ovarian tumours are grouped by the type of cells that the cancer starts in.

Epithelial ovarian carcinoma starts in epithelial cells. It is the most common type of ovarian cancer. Serous carcinoma is the most common type of epithelial ovarian carcinoma.

Many serous ovarian carcinomas are now thought to come from cells from the nearby fallopian tube that have implanted on the surface of the ovary.

Tumours of borderline malignancy also start in the epithelial cells. They share some, but not all features of carcinomas under the microscope. They do not usually spread into nearby tissues or other parts of the body. Examples of tumours of borderline malignancy are serous tumours and mucinous tumours.

Stromal tumours start from stromal cells. Granulosa cell tumours are the most common type of stromal tumour that can be malignant.

Germ cell tumours start in germ cells. Mature cystic teratoma (dermoid cyst) is the most common type of ovarian tumour overall. It is usually non-cancerous. The most common type of cancerous germ cell tumour is dysgerminoma.

Primary peritoneal serous carcinoma can develop in the peritoneum, which is the membrane that lines the walls of the abdomen and pelvis. It is similar to epithelial ovarian cancer, but there is very little or no cancer in the ovary and it isn’t clear where the cancer started.

Changes to cells in the ovary don’t always lead to cancer. Changes to the cells may lead to non-cancerous conditions such as cysts. They can also lead to non-cancerous tumours such as an adenofibroma.

The ovaries

The ovaries are the organs in a woman’s reproductive system that produce eggs (ova). There are 2 of them, and they are deep in a woman’s pelvis, on both sides of the uterus (womb), close to the ends of the fallopian tubes.

Diagram of the female reproductive system
Diagram of the female reproductive system

Structure

The ovaries are made up of 3 different types of cells:

Epithelial cells make up the outer layer covering the ovary (called the epithelium).

Germ cells are inside the ovary. They develop into eggs.

Stromal cells form the supportive or connective tissues of the ovary (called the stroma).

A thin layer of tissue called the capsule surrounds each ovary.

Diagram of the cross-section of the ovary
Diagram of the cross-section of the ovary

Function

The ovaries have 2 main functions. They make the female sex hormones and they produce mature eggs.

The female sex hormones are estrogen and progesterone. The ovaries are the main source of these hormones.

 

Estrogen is the main female sex hormone. It is responsible for the development of a woman’s breasts, body shape and reproductive organs.

Progesterone prepares the body for conception by causing the buildup of the uterine lining (endometrium) and regulates menstruation and pregnancy.

Each month during ovulation, an ovary releases a mature egg. The egg travels down the fallopian tube to the uterus. If it is fertilized by a sperm, the egg attaches itself (implants) to the lining of the uterus and begins to develop into a fetus. If the egg is not fertilized, it is shed from the body along with the lining of the uterus during menstruation.

During menopause, the ovaries stop releasing eggs and producing sex hormones.

Expert review and references

  • American Cancer Society. Ovarian Cancer. 2014: http://www.cancer.org/acs/groups/cid/documents/webcontent/003130-pdf.pdf.
  • American Society of Clinical Oncology. Ovarian, Fallopian Tube, and Peritoneal Cancer. 2016: http://www.cancer.net/cancer-types/ovarian-cancer/view-all.
  • Brown J, Jhingran A, Deavers M . Stromal tumors of the ovary. Raghavan D, Blanke CD, Honson DH, et al (eds.). Textbook of Uncommon Cancer. 4th ed. Wiley Blackwell; 2012: 36: 508-518.
  • Clement PD & Young RH. Atlas of Gynecologic Surgical Pathology. 3rd ed. Saunders Elsevier; 2014.
  • Eskander RN, Diaz-Montes TP, Vang R, Armstrong DK, Bristow RE . Borderline tumors and other rare epithelial tumors of the ovary. Raghavan D, Blanke CD, Honson DH, et al (eds.). Textbook of Uncommon Cancer. 4th ed. Wiley Blackwell; 2012: 35: 497-506.
  • Levine DA, Dizon DS, Yashar CM, Barakat RR, Berchuch A, Markman M, Randall ME. Handbook for Principles and Practice of Gynecologic Oncology. 2nd ed. Philadelphia, PA: Wolters Kluwer; 2015.
  • Martini FH, Timmons MJ, Tallitsch RB. Human Anatomy. 7th ed. San Francisco: Pearson Benjamin Cummings; 2012.
  • Matei DE, Schilder JM, Michael H . Germ cell tumors of the ovary. Raghavan D, Blanke CD, Honson DH, et al (eds.). Textbook of Uncommon Cancer. 4th ed. Wiley Blackwell; 2012: 37: 520-530.
  • Selman AE, Copeland LJ . Extraovarian primary peritoneal carcinomas. Raghavan D, Blanke CD, Honson DH, et al (eds.). Textbook of Uncommon Cancer. 4th ed. Wiley Blackwell; 2012: 34: 485-495.

Cancerous tumours of the ovary

Malignant tumours of the ovary are cancerous growths that have the potential to spread (metastasize) to other parts of the body. Malignant ovarian tumours are grouped by the type of cells that the cancer starts in.

Non-cancerous tumours and conditions of the ovary

A benign tumour of the ovary is a non-cancerous growth that does not spread (metastasize) to other parts of the body and is not usually life-threatening. Benign conditions of the ovary, such as cysts and polycystic ovaries, are also non-cancerous.