The mesentery is a type of connective tissue in the abdominal cavity that contains lymph nodes. Cancer sometimes arises from these nodes and is called mesenteric lymphoma. Because of the particular circulatory properties of the mesentery, mesenteric lymphoma, unlike most other lymphomas, frequently does not cause symptoms until the tumours have become quite large. Fortunately, there is a particular sign that appears on an abdominal CAT scan that is very specific for mesenteric lymphoma.
Anatomy of the Mesentery
The mesentery is a network of fatty connective tissue that suspends and connects some of the organs inside the abdomen. The mesentery is poorly supplied with blood and with vessels of the lymphatic system. It does contain some lymph nodes, and so tumours can occasional grow in them. Because of the poor circulatory connection with the rest of the body, mesenteric lymphoma often does not cause the constitutional symptoms typical of other lymphomas, per Harrison's Principles of Internal Medicine.
Constitutional Symptoms of Lymphoma
Other lymphomas frequently cause weight loss, low-grade fever, night sweats, fatigue and malaise. These symptoms usually occur before lymph nodes become noticeably swollen or painful, and are often what bring lymphoma patients in to see the doctor. They are caused by the release of chemical signals, called cytokines, from the tumour into the blood stream and lymph system. Because the mesentery is poorly connected with these systems, cytokines often do not become widely disseminated in mesenteric lymphoma and these symptoms often do not occur.
Symptoms of Mesenteric Lymphoma
Most of the noticeable symptoms of mesenteric lymphoma result from the tumours becoming large enough to affect normal intestinal function. The most common complaint of patients with mesenteric lymphoma is abdominal pain, sometimes accompanied with nausea, vomiting or constipation. The pain is usually diffuse, and often described as being deep within the abdomen. Sometimes a patient may even notice an unusual lump in the abdomen.
The Sandwich Sign
A particular finding on an abdominal CAT scan is highly suggestive of a mesenteric lymphoma. It is called the "sandwich sign," because of the characteristic appearance of the darker "buns" of the tumour enclosing either side of a lighter middle region. This sign is highly characteristic of mesenteric lymphoma and is unlikely to arise from anything else.
Finding Mesenteric Lymphoma
Because mesenteric lymphomas can become quite large before causing symptoms, many tumours are found incidentally, while looking for something else. Frequently, an abdominal CAT scan will be performed for some other reason and the sandwich sign will show that there is mesenteric lymphoma present. Physicians have encountered mesenteric lymphomas incidentally during the course of unrelated abdominal surgery. Fortunately, these tumours usually do not spread aggressively and surgical removal is often an effective treatment.