What causes omentum cancer

Overview

Omentum cancer is a term often used to describe cancers that affect the omentum, a large fold of peritoneum that hangs down from the stomach and covers the intestines. Medically, it is more accurately referred to as primary peritoneal cancer or secondary peritoneal cancer. Primary peritoneal cancer originates within the peritoneum itself, while secondary peritoneal cancer involves the spread of cancer from another organ to the peritoneum, including the omentum. The omentum's extensive surface area and rich blood supply make it a common site for cancer cells to implant and grow.

What is the Peritoneum and Omentum?

The peritoneum is a serous membrane that forms a protective sac within the abdominal cavity. It has two layers: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which covers the abdominal organs. The omentum is a specialized fold of the peritoneum, consisting of the greater omentum and the lesser omentum. The greater omentum is a large, apron-like structure that hangs from the greater curvature of the stomach and extends down over the small intestine and transverse colon. It contains a significant amount of adipose tissue and plays a role in immune response and fat storage. The lesser omentum connects the stomach to the liver.

Causes and Risk Factors of Omentum Cancer

The exact cause of primary peritoneal cancer is unknown, but it shares many risk factors with ovarian cancer. This is because the cells of the peritoneum and the surface cells of the ovary are thought to originate from the same embryonic tissue.

1. Ovarian Cancer: The most significant cause of peritoneal cancer affecting the omentum is the spread from ovarian cancer. It is estimated that around 80% of women diagnosed with primary peritoneal cancer have a history or simultaneous diagnosis of ovarian cancer. The cancer cells detach from the ovary, spread across the peritoneal surface, and can implant on the omentum.

2. Other Cancers Spreading to the Peritoneum: Cancers originating in other abdominal organs can also spread to the peritoneum and the omentum. These include:

• Colorectal cancer: Cancer of the colon or rectum can metastasize to the peritoneum.
• Stomach cancer (Gastric cancer): Peritoneal carcinomatosis is a common late-stage complication of stomach cancer.
• Pancreatic cancer: The peritoneum is a frequent site for metastasis from pancreatic cancer.
• Appendix cancer: Although rare, appendix cancers, particularly mucinous adenocarcinomas, can spread extensively throughout the peritoneum.
• Other gastrointestinal cancers: Cancers of the small intestine, liver, and gallbladder can also spread.

3. Genetic Predisposition: Mutations in certain genes, particularly BRCA1 and BRCA2, are strongly associated with an increased risk of both ovarian and breast cancer, as well as primary peritoneal cancer. Individuals with a family history of these cancers may have a higher risk.

4. Age: Like most cancers, the risk of peritoneal cancer increases with age. It is more commonly diagnosed in older women, typically after the age of 50.

5. Hormonal Factors: Factors that increase the number of ovulation cycles, such as early menarche, late menopause, and never having been pregnant, are associated with an increased risk of ovarian and peritoneal cancers. This is linked to the theory that repeated ovulation may lead to damage and repair processes on the ovarian surface, increasing the chance of cancerous mutations.

Symptoms

Symptoms of omentum or peritoneal cancer are often non-specific and can mimic other common abdominal conditions, leading to delayed diagnosis. Common symptoms include:

• Abdominal pain or discomfort
• Abdominal swelling or bloating
• A feeling of fullness, even after eating small amounts
• Changes in bowel habits (constipation or diarrhea)
• Unexplained weight loss
• Nausea or vomiting
• Ascites (fluid buildup in the abdominal cavity)

Diagnosis

Diagnosis typically involves a combination of imaging tests, blood tests, and a biopsy. Imaging such as CT scans, MRI, and ultrasounds can help visualize the extent of disease. CA-125 is a tumor marker that is often elevated in peritoneal and ovarian cancers, though it is not specific. Definitive diagnosis requires a surgical procedure to obtain a tissue sample (biopsy) for pathological examination.

Treatment

Treatment depends on the primary source of the cancer and the extent of peritoneal involvement. For primary peritoneal cancer and advanced ovarian cancer with peritoneal spread, treatment often involves surgery (cytoreductive surgery) to remove as much visible tumor as possible, followed by chemotherapy, often delivered intraperitoneally (directly into the abdominal cavity) to target cancer cells on the peritoneal surfaces.