Omentum cancer is characterized by the presence of malignant cells within the omentum, a sheet of fatty tissue in the abdomen. This diagnosis is overwhelmingly associated with secondary cancer, meaning the malignant cells originated elsewhere and spread to this abdominal layer. Primary omentum cancer, where the disease starts in the omentum itself, is extremely rare. Understanding the nature of this tissue and its role in the spread of disease is crucial for addressing the symptoms and complex treatment pathways.
The Omentum: Anatomy and Function
The omentum is a large, apron-like fold of tissue that hangs down from the stomach and transverse colon, draping over the intestines and other abdominal organs. It is typically divided into the greater omentum, the large fatty sheet, and the lesser omentum, a smaller fold connecting the stomach and liver.
This tissue is rich in blood vessels, lymph vessels, and specialized immune cell clusters known as “milky spots.” These spots are concentrations of macrophages, lymphocytes, and other immune cells that survey the abdominal cavity for foreign material and infection. The omentum’s extensive vascular network and immunological function allow it to adhere to and seal off areas of inflammation or injury within the abdomen.
This environment, designed for defense and repair, makes the omentum a favorable site for cancer metastasis. The rich blood supply provides nutrients for rapid tumor growth, and the specialized cells and fat content promote the implantation and survival of circulating cancer cells. Cancer cells shed from a primary tumor often float in the peritoneal fluid and eventually implant in the omentum.
Understanding Cancer Origin
The vast majority of malignant tumors found in the omentum result from metastasis, or the spread of cancer from a primary source elsewhere. Cancer cells often disseminate through the peritoneal fluid, eventually reaching the surface of the omentum. This secondary involvement means the cancer is named for its original site, such as metastatic ovarian or gastric cancer.
Cancers most commonly responsible for spreading to the omentum originate in the abdominal and pelvic cavities, including ovarian, stomach, and colorectal cancers. Pancreatic and appendiceal cancers can also frequently spread here. Involvement of the omentum generally indicates a more advanced stage of the disease, reflecting its capacity to spread beyond the organ of origin.
In rare instances, a malignant tumor can arise directly from the cells within the omentum, defined as primary omental cancer. These primary tumors are exceptionally uncommon. Examples of these rare primary malignancies include various types of sarcomas, such as liposarcoma and leiomyosarcoma, or mesothelioma.
Symptoms and Diagnosis
Symptoms of omentum involvement are often vague and can mimic other gastrointestinal conditions, potentially leading to a delay in diagnosis. Common signs relate to the mass effect of the growing tumor or resulting fluid accumulation in the abdomen. Patients frequently report non-specific abdominal discomfort or pain.
Noticeable symptoms include a feeling of fullness after eating only a small amount of food, known as early satiety, and unexplained weight loss. As the disease progresses, patients may experience a noticeable increase in abdominal girth or distention, sometimes accompanied by a palpable mass. This swelling is often caused by ascites, the buildup of excess fluid in the peritoneal cavity due to the cancer’s presence.
Diagnosis typically begins with imaging studies to visualize the abdominal cavity and identify any masses. A Computed Tomography (CT) scan is often the preferred modality because it provides detailed anatomical information and can help identify the primary site of the cancer. Magnetic Resonance Imaging (MRI) may also be used for detailed tissue characterization.
Blood tests for tumor markers, such as CA-125, may be conducted, particularly when ovarian cancer is suspected as the primary source. However, these markers alone are not definitive for diagnosis. Definitive confirmation of omental cancer requires a biopsy, where a tissue sample is taken and examined by a pathologist. This sample may be collected via a needle biopsy or, more often, during exploratory surgery to ensure adequate material is obtained.
Comprehensive Treatment Approaches
Treatment for omental cancer, particularly when metastatic, is designed to reduce the tumor burden and manage the disease, often involving a combination of surgery and chemotherapy. The goal is frequently cytoreduction, meaning removing as much of the visible tumor as possible to improve the effectiveness of other therapies. This approach is tailored to the primary cancer type and the extent of the spread.
The primary surgical intervention is an omentectomy, the removal of the omentum itself. This procedure can be a partial removal or a total (supracolic) removal of the entire fatty apron. An omentectomy is often performed as part of a larger cytoreductive surgery, which involves removing other visible disease from the abdominal organs and lining.
Routine omentectomy is recommended during cytoreductive surgery for peritoneal surface malignancies because a significant number of patients have occult, or hidden, microscopic cancer cells in the tissue. Studies show that more than 30% of grossly normal-appearing omenta contained microscopic metastasis. Furthermore, removing the omentum does not appear to increase the overall complication rate of the surgery.
Chemotherapy is a standard part of the treatment plan and may be administered systemically (intravenously) or through a specialized regional approach. A specific treatment option often used for omental disease is Hyperthermic Intraperitoneal Chemotherapy (HIPEC). During HIPEC, a heated, sterile chemotherapy solution is circulated directly within the abdominal cavity for a short period immediately following cytoreductive surgery. This technique aims to destroy any remaining microscopic cancer cells, capitalizing on the cancer cells’ sensitivity to heat and the direct, high concentration of the drug.