What is the Omentum and Why is it Important in Cancer?

Omentum Function and Role in Metastatic Ovarian Cancer

Medicine: Human body, Great omentum, illustration
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Definition: Omentum

The omentum is a large fatty structure which literally hangs off the middle of your colon and drapes over the intestines inside the abdomen.

Anatomy and Structure

The omentum is a 2 layered structure that is like a parachute that covers and surrounds the organs of the abdominal cavity.  It's consistency is somewhere between that of lumpy linen and jello. It is broken down into 2 parts, which in adults are mostly fused together.

  • The greater omentum - The greater omentum hangs own from the stomach.
  • The lesser omentum - The lesser omentum hangs down from the liver.

Purpose and Function of the Omentum

It is not clear why it was designed as part of the human body, but it does reach every organ in the abdomen, draping over and attaching itself to areas of inflammation.  So, as part of its function, it may act as a bandage in case of bad infection or intestinal rupture (such as appendicitis), limiting spread of infection.  Some possible functions include:

  • Maintaining the positions of organs in the abdomen, including keeping the intestines and stomach near the liver.
  • Acting as a storage depot for fat (see abdominal obesity below.)

The Omentum and Ovarian Cancer Metastases

  The omentum is important in ovarian cancer because it has a lot of tiny blood vessels. So cancer cells that have broken away from the ovary like to implant and grow there, known as omental metastasis.

  The omentum also has a rich supply of lymphatic or immune areas known as "milky spots."

The omentum becomes very important in advanced ovarian cancer when debulking or cytoreduction surgeries are performed.  These surgeries are done to remove as much cancer as possible, so there is less cancer left to treat with chemotherapy.

  When much of the cancer is removed, there is a greater chance that chemotherapy will be able to get rid of as much cancer as possible before the cancer cells become resistant to the chemotherapy drugs used.

Understanding the structure of the omentum makes is easier to understand why this debulking surgery is so difficult.  Small clusters of cancer cells can be interspersed throughout this extensive area, which are difficult to remove with all of the blood vessels in the area as well.  It is a tedious and time consuming surgery that takes great precision.  Meanwhile, the surgical time is limited by a patient's ability to withstand an extended period of time under general anesthesia.  In order to get optimal cytoreduction, the surgery can take many hours.

Other Conditions involving the Omentum

Several other conditions are related to the structure and function of the omentum include:

  • Abdominal obesity - The omentum acts as a storage area for fat.  When there is excessive storage of fat in the omentum, people develop an apple shaped body form known as abdominal obesity.  This is referred to by many people as belly fat.  Abdominal fat is one of the risk factors for metabolic syndrome of syndrome X.  People with this syndrome are at a higher risk of developing heart disease at a young age.
  • Adhesions - Abdominal adhesions, or scar tissue that forms throughout the omentum in response to abdominal surgery, infections, or inflammatory conditions involving the omentum can be a very serious condition.  It is a common cause of emergency abdominal surgery for bowel obstructions and can be a cause of infertility and chronic pain.

Pronunciation: oh-men-tum

Also Known As: omental cake, epiplon

Examples: During surgery, the omentum was found to contain multiple cancerous tumors.


Koppe, M., Nategaal, I., de Wilt, J., and W. Ceelen. Recent insights into the pathophysiology of omental metastases. Journal of Surgical Metastases. 2014. 110(6):670-5.

Sorensen, E., Gerber, S., Sedlacek, A., Rybalko, V., Chan, V., and E. Lord. Omental immune aggregates and tumor metastasis within the peritoneal cavity. Immunologic Research. 2009. 45(2-3):185-94.

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