Mesenteric tumors are uncommon lesions that are generally considered inclusive of similar lesions of the omentum. Primarily anecdotal references to this class of tumors have been made since the beginning of the 20th century. In 1936, Hart provided the earliest clear description of solid mesenteric tumors. As experience has accumulated in treating these lesions, a more complete picture of the various disease types that manifest as mesenteric masses has emerged.
Mesenteric tumors may be cystic or solid, and they may demonstrate malignant or benign clinical behavior. Although uncommon, they are encountered in all age groups from infancy to the very elderly. These tumors should be considered as an explanation for a palpable abdominal mass, but they are most commonly brought into the differential diagnosis of abdominal pathology once a suggestive radiologic study or an abdominal operation has been performed. An increased awareness of neoplastic and nonneoplastic processes that result in mesenteric masses aids the clinician in recognizing these diseases.
This article discusses mass lesions of the mesentery, including nonprimary tumors with manifestations related to the mesentery. The image below illustrates a lesion that was discovered incidentally.
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This small, well-circumscribed lesion of small-bowel mesentery caused no symptoms and was incidentally discovered at operation.
The mesentery of the gastrointestinal (GI) tract consists of a contiguous, fibrofatty, fanlike structure containing arterial, venous, lymphatic, and neural structures coursing to and from the intestine, along the intestine's entire length.
The small-bowel mesentery and portions of the large-bowel mesentery are mobile within the peritoneal cavity. The mesenteries of the ascending and descending colon become fixed against the retroperitoneum during the normal course of fetal development. The lesser omentum is also technically a mesentery, and any consideration of tumors of these structures is generally inclusive of lesions of the greater omentum as well.
The vast majority of reported mesenteric tumors originate in the small-bowel mesentery or omentum.
Clinical findings and symptoms associated with mesenteric tumors of all types are related to the presence of a mass lesion. Because the mass does not involve the tubular portion of the GI tract per se, obstructive symptoms are generally late findings in malignant mesenteric tumors and large benign tumors.
Without question, pain is the principal manifestation of mesenteric masses in adults and older children. A visceral pattern of pain may be related to mass effect within the peritoneum or to traction on the mesentery. This is generally deep and poorly localized discomfort, frequently described as central within the abdomen.
Benign mesenteric masses
These lesions are almost exclusively found in the mesentery of the small intestine, though cysts of the colonic mesentery have also been described. Most are lymphangiomas,[1, 2] but simple peritoneal cysts and enteric cysts are also found, as well as rare mesenteric mesotheliomas with prominent cystic components.
Primary lipoblastoma of the mesentery has been reported in infants and in children as old as 12 years. This benign tumor of fetal-embryonal fat tissue is generally recognized when an abdominal mass is palpated on physical examination. It is very amenable to surgical excision, though local recurrence has been described. Other benign neoplasms of the mesentery are exceedingly rare, but tumors of neural origin, hamartomas,[3] and stromal tumors of small size with nonaggressive clinical behavior have been described.
Malignant mesenteric tumors
A relatively few tumor types account for the vast majority of mesenteric malignancies; in these malignancies, the small-bowel mesentery is almost exclusively the site of involvement.
Primary malignant mesenchymal or stromal tumors of the mesentery of the bowel (see the image below), as well as of the greater and lesser omentum, are a rare subset of abdominal cancers that resemble either retroperitoneal sarcomas or GI stromal tumors (GISTs) primary to the intestine.[4, 5, 6] Most of these have been described as leiomyosarcomas.[7, 8] Miettinen et al reported that in a group of 26 cases analyzed by the Armed Forces Institute of Pathology, the incidence of omental and mesenteric tumors was roughly equal.[9]
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Computed tomography (CT) scan of mesenteric stromal tumor (circled area). Shown is infiltrative lesion surrounding vascular structures within proximal....
Characterization of protein markers of this tumor type has indicated that they are phenotypically very similar to the GIST group and are less often phenotypically related to retroperitoneal leiomyosarcomas. The absence of a detectable primary intestinal tumor signifies a primary mesenteric origin of the lesion.
Patients with mesenteric tumors exhibit signs and symptoms of intestinal obstruction; however, in contrast to primary tumors of the intestine, much bulkier disease may be present before obstructive findings are encountered.
Desmoid tumors of mesentery
Mesenteric desmoid tumors are a relatively infrequent but potentially life-threatening complication of familial adenomatous polyposis (FAP).[10, 11] These tumors are areas of progressive fibroblastic and fibrous proliferation within the mesentery (and, less frequently, the retroperitoneum) that can locally involve vascular structures and can constrict and obstruct the bowel. Although described as histologically benign lesions, their infiltrative pattern of growth can ultimately lead to life-threatening patterns of visceral involvement.
Sporadically occurring desmoid tumors are more numerous than those observed in FAP, though the cumulative risk of the development of these lesions is far greater in patients with FAP. Mesenteric desmoid tumors were originally reported as a component of Gardner syndrome, a phenotypic pattern of FAP that, in addition to intestinal adenomatous polyps, is also associated with bony abnormalities, pigmented ocular fundus lesions, and cutaneous epidermoid cysts and fibromas. That such arbitrary classifications are not necessarily valid is now apparent.
Although a causative relationship in desmoid formation has not been firmly established, various mutations of the APC gene have been identified in these tumors.[12] Desmoid tumors are more frequently associated with disease-causing mutations distal to codon 1444 of the APC gene.
Mesenteric lymphoma
Primary mesenteric lymphoma, in contrast to primary small-bowel lymphoma, is a disease of the mesenteric lymph nodes that may represent a localized process or a component of a more disseminated pattern of disease. The clinical presentation of mesenteric lymphoma is much like that of other mesenteric tumors, with abdominal pain and palpable mass as the principal findings.
Computed tomography (CT) can characterize the lesion from the standpoint of size and mesenteric location and can raise the probability of the lymphoma diagnosis. The follicular centroblastic-centrocytic histologic type of lymphoma has been shown to predominate at mesenteric sites.[13] A few cases of mesenteric lymphomas observed in association with immune thrombocytopenia and dermatitis herpetiformis have been reported.
The vast majority of metastatic lesions of the mesentery consist of mesenteric lymph nodes that have become secondarily involved in a neoplastic process of the tubular GI tract. Distinguishing this pattern of tumor growth from primary mesenteric tumors usually presents no difficulty because the GI primary tumor site is usually readily identifiable.
Mesenteric carcinoid tumors
Carcinoid tumors of the small intestine are metastatic to mesenteric lymph nodes at the time of diagnosis in 40-50% of patients, though almost all such tumors that are greater than 2 cm in diameter have associated nodal involvement. Of these, a small subset may have minimal obvious disease within the small intestine and large mesenteric nodal metastases that may account for the vast majority of the tumor burden. In addition, primary mesenteric carcinoids have been described that have been assumed to arise de novo in mesenteric tissues, though the veracity of this assumption is uncertain.
This pattern of disease may be accompanied by extrinsic compression and occlusion of mesenteric arterial blood supply and segmental ischemia or infarction of the intestine. Extensive carcinoid tumor involvement of small-bowel mesentery has been reported in association with a malabsorption syndrome.
Mesenteric lipodystrophy
Mesenteric lipodystrophy (retractile mesenteritis, mesenteric panniculitis) is a rare condition that can be mistaken for a mesenteric neoplasm on the basis of clinical, radiologic, and gross characteristics. It is a mesenteric thickening or mass that can be nodular in consistency and either focal or diffuse within the small-bowel mesentery. The root of the mesentery and the tissues surrounding the superior mesenteric vessels are invariably involved.
The mass may consist of hypertrophied fatty tissue, dense fibrous tissue, fat necrosis, or combinations of these, along with a nonspecific chronic inflammatory infiltrate. Its presenting symptom is abdominal pain in most patients, though it has been anecdotally reported in association with fever, mesenteric calcifications, and protein-losing enteropathy.
The causative agents are unknown, though an association with lymphoma has been reported. Current data indicate that the condition is nonprogressive and presents no significant danger to the patient.
Treatment is nonsurgical (though the diagnosis is confirmed on operative biopsy) and generally supportive. In patients with more severe symptoms, antimetabolites such as cyclophosphamide have been associated with a decrease in lesion size and with symptom relief. Other reportedly beneficial agents include steroids, colchicine, and tamoxifen.
Mesenteric lymphadenopathy
Infectious etiologies of mesenteric lymph node enlargement include bacterial infection, mycobacterial infection, and histoplasmosis. A large number of these cases have been reported since the onset of the HIV epidemic. Although lymphadenopathy is usually generalized in tuberculosis, mesenteric lymphadenitis has been described as the principal presenting problem.
Castleman disease (giant lymph node hyperplasia) is a rare condition usually observed in the mediastinum. However, cases of isolated mesenteric disease have been reported. These primarily occur in women and can be associated with iron malabsorption and anemia. Sarcoid has been reported as a cause of localized bulky mesenteric lymphadenopathy.
No known etiologic or associated diseases have been reported in cases of primary mesenteric neoplasms. Reactive lymphadenopathy within the mesentery may be a manifestation of systemic, often infectious, disease.
Solid primary tumors of the mesentery are rare. Published reports have consisted of small numbers of cases, which makes it difficult to determine the incidence of specific tumor types. Reasonable estimates of incidence range from 1 case per 200,000 to 1 case per 350,000 population. Mesenteric tumors have been described as cystic in 40-60% of cases.[14]
Numerous anecdotal reports of mesenteric lipomas in adults and children have appeared over the years, suggesting that these probably represent the most frequently encountered symptom-causing solid tumors of primary mesenteric origin.
Malignant primary mesenteric tumors are extremely uncommon, even compared with primary malignancies of the small bowel. Published reports suggest that one third to one half of all mesenteric masses are malignant tumors. The largest case series have been from France and China.[15, 16]
These reports indicate that approximately two thirds of malignant mesenteric tumors are mesenchymatous (most characterized as leiomyosarcoma or liposarcoma), while the remainder are primarily lymphomas.
Cook et al, using Surveillance, Epidemiology and End Results (SEER) program data, calculated male-to-female incidence rate ratios (IRRs) for various cancers for the period between 1975 and 2004.[17] According to their results, mesenteric cancer occurred more frequently in females than in males, with the overall male-to-female IRR for cancers of the peritoneum, omentum, and mesentery being 0.18.
The results of surgical treatment of benign cysts and solid tumors of the mesentery are very favorable. This is true of even large benign tumors, though local recurrence has been reported. Death as a consequence of benign masses, with the exception of mesenteric desmoid tumors, can be assumed to be an extremely unlikely event.
Because so few cases have been reported, long-term results of surgical treatment of malignant mesenteric mesenchymal tumors have not been well characterized. In fact, no large series reporting management and outcomes of treatment of this tumor type have been conducted. Published reports suggest that their biologic behavior is similar to that of primary GI mesenchymal malignancies. Reported sites of hematogenously spread metastases include the liver and lungs.
Extrapolation of the results of treatment of similarly staged GI stromal malignancies suggested that 5-year survival rates were in the range of 20-50%. A study of 114 mesenteric GISTs by Feng et al reported a 5-year disease-free survival rate of 57.7% and a 5-year disease-specific survival rate of 60.1%.[18] No specific postoperative adjuvant or palliative therapies, such as cytotoxic chemotherapy or radiation therapy, have been shown to be of benefit.
Intra-abdominal desmoid tumors are the second most frequent cause of death in FAP patients (after cancer-related deaths).
Pain is the principal presenting symptom resulting in the discovery of a mesenteric mass. A palpable mass may also be present, although generally not without some abdominal pain. Nausea, vomiting, diarrhea, bloating, and constipation have also been described with mesenteric tumors.
Although most symptoms reflect a fairly indolent process, intestinal obstruction has been reported with benign and malignant mesenteric tumors. In the case of malignant tumors, this is generally secondary to aggressive local growth. In the case of benign tumors such as lipoma, the pathophysiology of obstruction is more complex.
Published descriptions of obstruction with mesenteric lipoma have implicated small-bowel encasement, small-bowel volvulus, or tumor infarction and obstruction due to the consequent inflammatory mass. Acute appendicitis as the result of torsion of a mesoappendiceal lipoma has also been described.
Clinical examination may reveal an abdominal mass. In the case of mesenteric lipoma, the tumor frequently cannot be appreciated by palpation.
In the case of mesenteric cysts, physical examination findings may reveal a mass lesion that is mobile only from the patient's right to left or left to right (Tillaux sign), in contrast to the findings with omental cysts, which should be freely mobile in all directions.
Radiologic characterization of malignant mesenteric tumors generally requires computed tomography (CT), which can provide important information regarding size and involvement of adjacent structures, as well as some tissue characteristics of the tumor.[19] (See the image below.) The localization of a mass to mesentery is generally possible with this study. CT can also distinguish between solid and cystic masses and can identify hepatic metastases in the presence of advanced malignant disease.
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Computed tomography (CT) scan of mesenteric stromal tumor (circled area). Shown is infiltrative lesion surrounding vascular structures within proximal....
Abdominal CT can be strongly suggestive of the diagnosis of lipoma as opposed to other solid tumors, though liposarcoma cannot be completely excluded on the basis of appearance on CT. These lesions have the density of fat and may surround mesenteric vessels and lymph nodes. To some extent, tumor vascularity can also be characterized with the administration of intravenous contrast during imaging.
Magnetic resonance imaging
Magnetic resonance imaging (MRI) is sometimes used in conjunction with CT to help characterize mesenteric masses. It provides information similar to that provided by CT but can also define tissue characteristics (ie, fatty vs fibrous) with greater sensitivity. No studies have compared CT with MRI in the examination of mesenteric masses; however, MRI may be of great value, particularly in patients with mesenchymal tumors. Diffusion-weighted sequencing may improve detection of mesenteric small-bowel tumors in comparison with standard unenhanced MRI enterography.[20]
Arteriography
Arteriography is seldom used as a preoperative study in patients with mesenteric tumors unless there is a significant possibility that vascular involvement by the tumor may greatly complicate operative management. This procedure may define areas of mesenteric arterial blood supply that are compromised by tumor and may suggest the need for either extensive bowel resection with the mesenteric mass or arterial reconstruction.
Ultrasonography
The successful use of ultrasonography (US) to characterize mesenteric masses is well described. US is employed far less frequently in this setting than CT is, largely because of operator-dependent issues that can influence study consistency.
The presence of any solid mass lesion of the mesentery that is not thought to be a reactive lymph node or lymphoma is an indication for surgical removal. The inability to exclude malignancy definitively makes prolonged observation and repetitive studies an ill-advised management strategy.
In selected circumstances, biopsy is indicated to help confirm the diagnosis of certain lesions. For example, lymphoma might represent a likely diagnosis on the basis of radiologic findings. If no other more readily accessible tissues were available, it would be necessary to obtain mesenteric tissue to guide therapy.
A small simple cyst of the mesentery discovered incidentally can be observed. In the setting of interval enlargement, significant symptoms (generally pain), or evolution of symptoms, surgical excision is advisable for simple cysts as well. Complex cystic structures related to the omentum must prompt consideration of the possibility of a neoplastic process.
The use of laparoscopic methods to investigate and treat mesenteric masses is an evolving area of surgical care. In patients whose disease must be distinguished only from that requiring resection (ie, lymphoma, mesenteric lipodystrophy), laparoscopy offers a method of obtaining tissue for diagnostic purposes without subjecting the patient to a full laparotomy incision.
In general, effective medical treatment for neoplastic mesenteric masses is not available. Pain and other gastrointestinal complaints can be treated with analgesics and antiemetics, but these agents do not affect the underlying disease.
Mesenteric lymphoma is treated by cytotoxic chemotherapy. Mesenteric desmoid tumors reportedly respond to sulindac therapy, hormonal manipulation, and cytotoxic chemotherapy.[10, 21]
In general, surgical treatment of benign mesenteric masses consists of local excision for smaller lesions and resection for bulkier tumors, provided that the blood supply to the gut is not jeopardized. Although the bowel can be preserved in most circumstances, resection can be quite treacherous, depending on the relationship of the lesion to larger branches of the superior mesenteric artery. Most cystic mesenteric lesions can be easily excised. Resection of small intestine is rarely indicated for this problem.
Approaches to different tumor types
Malignant mesenteric tumors
Surgical treatment is the only therapy of demonstrated benefit for these tumors. The goal of surgical treatment is removal of gross disease with a margin of normal tissue. This requires resection of any involved intestine, as well as any intestine robbed of mesenteric arterial blood supply by the dissection to remove the tumor. As in the treatment of intestinal stromal tumors or retroperitoneal sarcomas, operative management may involve en-bloc resection of other involved structures.
Mesenteric desmoid tumors
These are very difficult lesions to treat surgically. Surgical treatment may increase recurrence risk, because it has been observed that desmoid tumors generally occur after abdominal surgery. Surgical debulking may be dangerous and ultimately unsuccessful and is generally reserved for patients with intestinal obstruction.[10, 11]
Mesenteric lymphoma
In contrast to primary small-bowel lymphoma, for which surgical treatment may play a valuable role in selected cases, mesenteric lymphoma is best treated with combination chemotherapy. Although some cases are diagnosed after resection of an uncharacterized mesenteric mass, surgical treatment is best used as a diagnostic tool when the diagnosis is probable but uncertain. Laparoscopy may play an important role when procurement of tissue for diagnostic purposes is the operative goal.
Mesenteric carcinoid tumor
This pattern of disease is treated by surgically resecting the mesenteric masses. This procedure should be performed en bloc with any extant primary intestinal tumor. Resection of mesenteric disease should be accomplished without endangering the blood supply to normal bowel, except in the immediate area of the disease. A primary carcinoid tumor, which may be quite small and multicentric, is generally found in the resected intestinal specimen.
Castleman disease
Because this problem is nonneoplastic and generally localized, treatment consisting of resection of the lymph node mass has had good results. Successful treatment via a laparoscopic approach has been reported.[22]
Operative details
At exploration, the mass is generally found to be completely contained within the mesentery. In the case of liposarcoma, encasement of the bowel with fatty tumor tissue can occur (see the image below).
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Resected mesenteric liposarcoma specimen. This firm, fatty mass replaced large-segment of small bowel mesentery and surrounded short segment of ileum ....
The gross extent of the tumor must be carefully defined in order to obtain clear margins of resection. Definition of proximity to large mesenteric blood vessels is vital. Normal intestine should be preserved to the greatest extent possible while good oncologic surgical principles are still observed. If resection requires so much intestine to be removed that maintenance of nutrition cannot be expected, the patient's clinical situation (eg, age, general health) must be taken into consideration before the operation proceeds.
Complications of surgical treatment of mesenteric masses are not specific to the disease type, except when extensive resection of solid tumors may endanger the mesenteric blood supply or when extensive small-bowel resection is necessary to remove the disease. Although short-bowel syndrome is an infrequent occurrence in surgery involving the mesentery, appropriate precautions must be taken to prevent this condition, which can result from overresection or from inadvertent damage to the blood supply to otherwise normal bowel.
Neal E Seymour, MD, Professor, Department of Surgery, Tufts University School of Medicine
Disclosure: Nothing to disclose.
Specialty Editors
Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Received salary from Medscape for employment. for: Medscape.
Amy L Friedman, MD, Professor of Surgery, Director of Transplantation, State University of New York Upstate Medical University College of Medicine, Syracuse
Disclosure: Nothing to disclose.
Chief Editor
John Geibel, MD, MSc, DSc, AGAF, Vice Chair and Professor, Department of Surgery, Section of Gastrointestinal Medicine, Professor, Department of Cellular and Molecular Physiology, Yale University School of Medicine; Director of Surgical Research, Department of Surgery, Yale-New Haven Hospital; American Gastroenterological Association Fellow; Fellow of the Royal Society of Medicine
This small, well-circumscribed lesion of small-bowel mesentery caused no symptoms and was incidentally discovered at operation.
Computed tomography (CT) scan of mesenteric stromal tumor (circled area). Shown is infiltrative lesion surrounding vascular structures within proximal jejunal mesentery.
Computed tomography (CT) scan of mesenteric stromal tumor (circled area). Shown is infiltrative lesion surrounding vascular structures within proximal jejunal mesentery.
Resected mesenteric liposarcoma specimen. This firm, fatty mass replaced large-segment of small bowel mesentery and surrounded short segment of ileum (lower edge of specimen). Principal presenting problem was partial small-bowel obstruction.
This small, well-circumscribed lesion of small-bowel mesentery caused no symptoms and was incidentally discovered at operation.
Computed tomography (CT) scan of mesenteric stromal tumor (circled area). Shown is infiltrative lesion surrounding vascular structures within proximal jejunal mesentery.
Resected mesenteric liposarcoma specimen. This firm, fatty mass replaced large-segment of small bowel mesentery and surrounded short segment of ileum (lower edge of specimen). Principal presenting problem was partial small-bowel obstruction.
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