Mesenteric Tumors - An Overview

What Is a Mesentery?

The mesentery acts as a framework for the small intestine to hold its shape and stay in its place in the abdominal cavity. The small intestine starts with the duodenum, which is on the right side of the abdomen due to the curvature of the stomach. The duodenum bends downwards and towards the left in the shape of a horseshoe to give rise to the jejunum, which is around 2.5 meters long and is folded into four distinct layers.

Next is the ileum, which is three meters long and is folded into five layers. The duodenum, jejunum, and ileum combine to form the small intestine. These folds are essentially suspended in the abdominal cavity; the mesentery provides them the framework to hold on to so that they can maintain their position. The mesentery is not just a framework. It also holds the blood, nerve, and lymph vessels that supply blood to the small intestine. At the location of the small intestine, the peritoneum (inner abdominal lining) forms a stalk-like structure called the root of the mesentery and is around 15 cm. The root divides superiorly in the shape of a Japanese hand fan to which the folds of the small intestine attach themselves; this continuous fanned-out membrane is known as the mesentery.

What Are Mesenteric Tumors?

Mesenteric tumors are a heterogeneous group of lesions found in the mesentery; they can be solid or cystic and benign or malignant. The mesenteric masses can be of different types because, like an organ, the mesentery also has nerve, blood, and lymph supply. An infection or malignancy can arise from these structures and trigger cellular proliferation. Based on the origin, the mesenteric tumors can be divided into-

1. Tumors of Lymphatic Origin - Can be further divided into-

• Cystic Lymphangioma - Occurs due to the failure of the lymphatic vessels to develop drainage into the lymphatic system before birth, leading to dilation of the lymphatic vessels (lymphangiectasia). These enlarged lymph vessels ultimately grow into cysts, which have a good chance of transforming themselves into malignant tumors. Symptoms are often non-specific and minimal; when present, the patient will have crampy abdominal pain and bowel obstruction.

• Lymphoma - It is the most commonly seen mesenteric tumor and almost always is non-Hodgkin's in nature. Advanced stage symptoms include fever, night sweats, and weight loss. Computed tomography (CT) will show a classic sandwich appearance of the lymphoma.

• Castleman's Disease - Often seen in patients infected with human immunodeficiency virus (HIV) and herpes virus. It is also an associated malignancy in patients suffering from Kaposi's sarcoma, Hodgkin's, and non-Hodgkin's lymphoma. Symptoms include general malaise, fever, anemia, and elevated CPR (C-reactive protein) levels.

• Metastatic Lymphadenopathy From Intestinal Neuroendocrine Tumor - The gastrointestinal tract (which starts with the mouth and ends with the anus) is the largest endocrine system in the body and the small intestine is the common site for endocrine tumors.

• Cancer cells from the small intestine metastasize to the mesentery and secrete growth factors which result in metastatic lymphadenopathy. Symptoms include bowel obstruction, portal hypertension, and mesenteric ischemia.

2. Primary Peritoneal Tumors - They can be further divided into-

• Simple Mesenteric Cyst - It is a birth defect and forms due to defects in the fusion of the peritoneum (inner abdominal lining). Small cysts are asymptomatic, and complications arise only when they enlarge.

• Benign Cystic Mesothelioma - Only seen in young women, and is often an associated complication in patients who have had abdominal surgery or an inflammatory disease. It is mostly seen in the pelvis with signs of aggressiveness and invasion of the adjacent organs.

• Malignant Peritoneal Mesothelioma - Seen in older men in their sixties and occurs due to exposure to asbestos. Unlike other tumors, which are localized and defined, malignant peritoneal mesothelioma is diffuse and indeterminate.

3. Tumors Originating From Fatty and Connective Tissue - They are divided into-

• Neoplasms - A neoplasm forms when the cells grow and divide more than they should. A few examples of mesenteric neoplasms are solitary fibrous peritoneal tumors, desmoid tumors, and fibromas.

• Tumors Arising From Mesenteric Fat - When fat is the origin of a tumor, it is termed lipoma; based on the rate of the tumor growth and its metastatic nature, it can be a benign lipoma, a liposarcoma, or a mesenteric/gastrointestinal stromal tumor.

4. Mesenteric Cellular Proliferation of Infectious and Inflammatory Origin - These are pseudotumors and form as a result of infection and inflammation; a few examples are myofibroblastic tumors, sclerosing mesenteritis, actinomycosis, and Whipple's disease.

5. Cystic Lesions of Extramesenteric Origin - These tumors arise from a location other than the mesentery but extend into the mesentery, mimicking a mesenteric tumor. Mucinous cystic tumors, non-pancreatic pseudocysts, and mature cystic teratomas are a few examples of cystic lesions of extra mesenteric origin.

The clinical history and associated symptoms should always be evaluated before finalizing the diagnosis.

What Type of Surgery Is Done for Mesenteric Tumors?

The type of surgery done depends on the nature of the lesion; for well-defined and well-circumcised tumors, a simple enucleation (complete removal of the contents along with the surrounding capsule) is sufficient.

For infiltrating tumors (tumors that have moved to the surrounding non-cancerous tissue), a wider resection is preferred to prevent a recurrence. Care is taken not to damage any underlying blood vessels and the root of the mesentery. In a few cases, tumor debulking is proposed, which entails the removal of as much of the tumor as possible in surgically incurable malignancies. Intestinal carcinoid with retractile mesenteritis is the classic example where tumor debulking is the only option.

What Are the Complications of the Surgery for Mesenteric Tumors?

Surgical removal of mesenteric tumors occasionally involves sacrificing part of the small intestine, which will lead to complications specific to the procedure; they are-

• Short Bowel Syndrome - It is a condition where the body is unable to absorb enough nutrients due to insufficient small intestine.

• Malabsorption Syndrome - Also a condition where the small intestine is unable to absorb nutrients but with associated symptoms like chronic diarrhea, abnormal tools, weight loss, and gas.

• Risk of Metastasis - In a few cases, surgery increases tumor cell dissemination which increases the survival chance of circulating cancer cells. These cells then travel to the surrounding organs and become deadlier than the primary lesion.

• Bowel Obstruction - As part of the healing process after surgery, the intestinal tissue, which is supposed to be smooth and moist, becomes fibrous and dry; this leads to food and liquids getting blocked in the small intestine.

Along with the above-mentioned complications, the risk of bleeding to the underlying blood vessels, infection, hemorrhage, etc., which are commonly seen in any surgery, is also applicable to surgery done for mesenteric tumors.

How Are Mesenteric Tumors Treated?

• A gastrointestinal surgeon diagnoses and treats the mesenteric tumors after sufficient investigations, which include ultrasound, magnetic resonance imaging (MRI), CT scan, and occasionally a fine-needle aspiration cytology (FNAC) test.

• These investigations also help to plan the treatment, and surgery is only done in tumors that are resectable. Surgery is the standard therapy for cystic lymphangioma, solitary fibrous tumors, mucinous cysts, desmoid tumors, and Castleman’s tumors.

• Complete resection without recurrence is possible in these lesions. However, in the case of malignant tumors, although resection with surgery is the primary goal of the treatment, it is always followed by chemo and radiation therapy, for example- malignant mesothelioma, liposarcoma, solitary fibrous tumor, etc.

• For the rest of the mesenteric tumors, chemo and medical therapy is the primary treatment. Medical therapy includes immunosuppressives, non-steroidal anti-inflammatory drugs, and supplementary hormones.

Conclusion:

Mesenteric tumors are relatively rare, and treating them is always complex due to their wide range of pathological entities. Treatment involves a multi-disciplinary approach with sufficient investigations. Careful planning, meticulous technique, and cooperative post-surgical follow-up will reduce the complications and improve the quality of life and chance of survival of the patient.