Approach Considerations
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 biopsy or excision, though observation and interval imaging have been advocated if there is a high suspicion of a mesenteric lipodystrophy diagnosis on the basis of computed tomography (CT) criteria. [33] The inability to exclude malignancy definitively for suspicious lesions makes prolonged observation and repetitive studies an ill-advised management strategy.
Image-guided core biopsy may be feasible and safe in appropriately selected cases. Otherwise, incisional biopsy is indicated to establish the diagnosis; this can frequently be accomplished laparoscopically. 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. A laparoscopic approach is frequently possible for this type of procedure (see the images below). Complex cystic structures related to the omentum must prompt consideration of the possibility of a neoplastic process.
Laparoscopic view of simple mesenteric cyst dissection bed after laparoscopic excision.
The use of laparoscopic methods to investigate and treat other mesenteric masses is an evolving area of surgical care. In patients whose disease must be distinguished from disease necessitating resection (eg, lymphoma or mesenteric lipodystrophy), laparoscopy offers a method of obtaining tissue for diagnostic purposes without subjecting the patient to a full laparotomy. At present, observation of good oncologic principles in approaching large lesions either known to be or suspected of being malignant requires laparotomy for proper local staging and operative planning.
Medical Therapy
Mesenteric masses and lymphadenopathy shown to be related to infection are best treated with appropriately directed antimicrobial therapy. Sclerosing mesenteritis has been treated with antimetabolites such as cyclophosphamide or azathioprine, which have been associated with a decrease in lesion size and with symptom relief. Other reportedly beneficial agents include corticosteroids, as well as colchicine, thalidomide, and tamoxifen alone or in combination with corticosteroids. [34, 35, 36]
The option of managing metastatic disease with palliative chemotherapy may be circumstantially necessary, with additional measures depending on response to treatment. Historically, chemotherapeutic regimens have not been effective for primary neoplastic mesenteric masses other than lymphoma. Pain and other gastrointestinal (GI) complaints can be treated with analgesics and antiemetics, but these agents do not address the underlying disease.
Targeted therapies have been investigated and encouraging results suggested for a variety of sarcoma types, including liposarcomas. [37, 38] Mesenteric soft-tissue sarcomas may generally be included in consideration of retroperitoneal sarcomas, and at present, it is not possible to cite specific results of targeted therapies for these.
Mesenteric lymphoma is treated with cytotoxic chemotherapy. Mesenteric desmoid tumors have been reported to respond to sulindac, hormonal manipulation, thalidomide, cytotoxic chemotherapy with doxorubicin-based combination regimens, and tyrosine kinase inhibitors, though results have generally been inconsistent or ultimately disappointing. [11, 39, 40] Radiation may be an option for unresectable, partially resectable, or recurrent mesenteric desmoid tumors—again, with inconsistent results. In a trial of the use of the protein kinase inhibitor sorafenib in patients with advanced desmoids, it was shown that the progression of disease could be slowed significantly. [41]
Surgical Therapy
In general, surgical treatment of benign mesenteric masses consists of local excision for smaller lesions. Most cystic mesenteric lesions can be easily excised. Resection of small intestine is rarely indicated for smaller benign tumors. One of the key goals of any operative approach is to preserve normal structures; however, resection can be quite treacherous, depending on the relation of the tumor to larger branches of the superior mesenteric artery. Surgical resection has the potential to be a major undertaking, with decision-making that involves consideration of en-bloc resection of visceral and vascular structures in order, ideally, to achieve negative surgical margins.
Approaches to different tumor types
Malignant mesenteric tumors
Surgical treatment is the therapy of greatest demonstrated benefit for these tumors. The goal of surgical treatment is removal of gross disease with tumor-free margins of resection. This can require en-bloc resection of any involved intestine, as well as any intestine that loses mesenteric arterial blood supply within the margins of resection needed to remove the tumor. As in the treatment of GI stromal tumors (GISTs) or retroperitoneal sarcomas, operative management may involve en-bloc resection of other involved structures. (See the images below.)
Mesenteric GIST-like tumor with solid and cystic components. Diagnosis was established after resection with demonstration of absence of primary GI tumor.
Resected mesenteric tumor. Operative treatment involved segmental small-bowel and colon resection. Large specimen size is evident.
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. [11, 12] There is some suggestion that multimodality treatment with with liposomal doxorubicin may be followed by a response sufficient to make previously unresectable disease resectable. [42]
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 can be localized, treatment should consist of local resection of the lymph node mass, which has had good reported results. Successful treatment using a laparoscopic approach has also been reported. [43]
Operative details
At exploration, initial steps generally involve characterization of disease on the basis of local and regional considerations, as well as pathology distant from the mesenteric mass. Masses may be completely contained within the mesentery, demarcated from surrounding tissues, or difficult to distinguish from normal surrounding mesenteric tissues. In the case of locally aggressive malignant masses such as liposarcoma, encasement of vascular structures or bowel with tumor tissue can occur (see the image below).
Section of malignant mesenteric fatty tumor resected en bloc with obstructed, encased small intestine.
The gross extent of the tumor must be carefully defined in order to identify clear margins of resection, which should be the goal of extirpative treatment. 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 in defining bowel segments for resection. If resection requires removal of so much intestine that maintenance of nutrition cannot be expected, the patient's clinical situation (eg, age and general health) must be considered before the resection is undertaken.
Complications
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-gut syndrome is an infrequent occurrence in surgery involving the mesentery, appropriate precautions must be taken to prevent this condition, which can result from excessive resection or from inadvertent damage to the blood supply of otherwise unaffected bowel. [1]
The difficulties associated with desmoid tumors for which surgery is undertaken raise particular concerns for complications such as bleeding and injury to involved or neighboring structures.
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Massive mesenteric cyst that proved to be multiloculated lymphangioma. This large but benign structure had developed on narrow attachment to base of small-bowel mesentery and was amenable to excision without endangering any other mesenteric structures.
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Cluster of enlarged lymph nodes (arrows) in small-bowel mesentery, which on laparoscopic biopsy proved to be B-cell (follicular) lymphoma.
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Mesenteric lymph node mass with metastatic involvement of small-bowel carcinoid. This was resected en bloc along with segment of small bowel within arterial blood supply distribution affected by removal of mass. This small intestine contained subcentimeter primary carcinoid tumor.
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Axial contrast-enhanced MRI of central hyperintense fatty mesenteric mass with preservation of fat around vessels and lymph nodes with "fat ring" or “halo” sign (arrows) consistent with mesenteritis. Courtesy of BioMed Central Ltd, Springer Nature [Arda K, Kizilkanat KT, Aydin H. CT and MRI aspect of mesenteric panniculitis. J Case Rep Med 7. 2018 Jun 30.]
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CT image of increased mesenteric tissue density or “misty mesentery” (between arrows), which laparoscopic incisional biopsy demonstrated was sclerosing mesenteritis.
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CT image of benign mesenteric lipoma. This discrete lesion (arrows) is homogeneous and has density of normal surrounding mesenteric fat.
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Laparoscopic view of simple mesenteric cyst before laparoscopic excision.
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Laparoscopic view of simple mesenteric cyst dissection bed after laparoscopic excision.
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Mesenteric GIST-like tumor with solid and cystic components. Diagnosis was established after resection with demonstration of absence of primary GI tumor.
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Resected mesenteric tumor. Operative treatment involved segmental small-bowel and colon resection. Large specimen size is evident.
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Section of malignant mesenteric fatty tumor resected en bloc with obstructed, encased small intestine.
