Omental mesothelioma is a rare occurrence, a cancer that arises in the mesothelial cells of the omentum. The omentum is a layer of fatty tissue that overlays abdominal organs and plays a role in the immune system. While peritoneal mesothelioma often invades the omentum, primary cancer here is extremely rare.
What is the Omentum?
The omentum is a layer of tissue that hangs like an apron over the front of the abdominal cavity. It develops out of mesothelial cells, the cells that make up the mesothelium in other parts of the body. The omentum consists of two layers of mesothelial tissue with fatty tissue, connective tissue, and a lot of blood vessels in between them.
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- The omentum contains several areas known as milky spots, which contain immune cells.
- Abdominal fluid circulates through the milky spots, which act as filters.
- The omentum adheres to foreign bodies, such as catheters, which can cause problematic blockages. This also helps seal off areas of inflammation or infection.
- When inflammation and infection occur, the immune cells in the omentum respond, destroying bacteria and foreign bodies.
- The milky spots provide immune cells to the abdominal cavity.
- The omentum stimulates the growth of blood vessels in the abdominal cavity to promote healing. Omental tissue can be used as grafts in other parts of the body to stimulate this growth.
Cancer in the Omentum
Malignancies arising in the omentum are rare. However, it is a site of metastasis and may even promote the spread of cancer. Because the fluid of the abdominal cavity circulates through the omentum, cancer cells can get trapped in it, proliferate, and easily develop new tumors.
What is Omental Mesothelioma?
Omental mesothelioma occurs when a primary tumor develops in the mesothelial cells of the omentum. It is extremely rare and has only ever been reported on in individual case studies. Peritoneal mesothelioma typically invades the omentum, but the cancer rarely originates there.
Symptoms of Omental Mesothelioma
With so few cases of this cancer recorded, usual symptoms are difficult to determine. Individuals in case studies had the following symptoms:
- Abdominal pain
- Back pain
- A tender mass in the abdomen
- Fluid buildup in the abdomen, known as ascites
- Weight loss
Diagnosis and Treatment of Omental Mesothelioma
The rarity makes it difficult to determine the best way to diagnose or treat this cancer. Misdiagnosis is common. Diagnosis follows the same steps as any cancer or mesothelioma, beginning with a physical exam.
This is followed by imaging scans and biopsies to confirm a malignancy and examine the cells to find the cancer type and area of origin of the primary tumor. Some patients may first receive a diagnosis of another type of cancer, such as peritoneal mesothelioma.
Treatment depends on each individual case, but in those studied, surgery was the primary treatment strategy. Some patients reported in case studies had the omentum removed and recovered. For others, the cancer was too widespread, and surgery could not eliminate all the tumors.
As with peritoneal mesothelioma, those with cancer in the omentum can benefit from palliative treatments: paracentesis to train uncomfortable fluid buildup, pain management, or surgeries to remove some of the cancerous tissue.
A Rare Case of Secondary Omental Mesothelioma
Just one case study exists of a patient who developed secondary omental mesothelioma after first being diagnosed with pleural mesothelioma. The pleural type of this cancer is aggressive and metastasizes readily, but not commonly into the abdomen or the omentum.
The case had several unusual features, including the fact that the man had never been exposed to asbestos. It is the first and only described case of pleural mesothelioma secondarily infiltrating the omentum.
The man had been treated for pleural mesothelioma followed by six months of stable disease. Then, the cancer spread to the right side of the pleura. Eleven months after that he had abdominal symptoms, including pain and ascites, the buildup of fluid. An ultrasound showed a mass in the omentum.
When doctors biopsied to get a sample of fluid and tissue, they were able to confirm that the mass was secondary mesothelioma. The cells showed the same pathology as those in the primary cancer.
A Rare Case of Mesothelioma of the Omentum and Liver
Yet another extremely rare example of omental mesothelioma is found in just one case study. This involved a woman, just 36 years old, who presented with abdominal and back pain. Doctors found masses on the liver and the omentum.
Pathology studies of the biopsied cells found that they both originated in the mesothelium. Unusual for mesothelioma, the cells were not rapidly dividing. The woman received a diagnosis of low-grade mesothelioma of the liver and omentum. Six months after surgical removal of the tumors, the woman showed no recurrence of cancer.
Omental mesothelioma is extremely rare, but it is possible and is probably associated with asbestos exposure. If you have exposure in your past, get screened regularly for any type of cancer.