DOI: 10.1148/rg.261055151
RadioGraphics 2006;26:245-264
From the Archives of the AFIP
Benign Fibrous Tumors and Tumorlike Lesions of the Mesentery: Radiologic-Pathologic Correlation1
Angela D. Levy, LTC, MC, USA,
Jordi Rimola, MD,
Anupamjit K. Mehrotra, MD and
Leslie H. Sobin, MD
1 From the Department of Radiologic Pathology (A.D.L.) and Department of Gastrointestinal and Hepatic Pathology (A.K.M., L.H.S.), Armed Forces Institute of Pathology, 6825 16th St NW, Washington, DC 20306-6000; Department of Radiology and Nuclear Medicine, Uniformed Services University of the Health Sciences, Bethesda, Md (A.D.L.); and Department of Radiology, UDIAT Diagnostic Center, Sabadell, Spain (J.R.). Received August 1, 2005; revision requested September 13 and received September 28; accepted September 28. All authors have no financial relationships to disclose.
Address correspondence to A.D.L. (e-mail: levya{at}afip.osd.mil).
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Abstract
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Mesenteric fibromatosis, sclerosing mesenteritis, inflammatory pseudotumor, and extrapleural solitary fibrous tumor constitute a loosely associated group of benign fibrous tumors and tumorlike lesions of the mesentery. These lesions are linked histologically by the presence of fibroblasts or fibrosis and anatomically by their location within the mesentery. Although rare, and distinctly different in pathogenesis and biologic behavior, these fibrous lesions have pathologic and radiologic features that overlap with one another and with more common neoplastic and nonneoplastic lesions of the mesentery. Mesenteric fibromatosis is a locally aggressive, benign proliferative process that may occur sporadically or in association with familial adenomatous polyposis. It most frequently manifests as a focal mesenteric mass and may simulate lymphoma, metastatic disease, or a soft-tissue sarcoma. Sclerosing mesenteritis is a rare idiopathic disorder that most commonly produces a stellate mass within the mesentery and should be differentiated from metastatic disease, specifically metastatic carcinoid, because it frequently responds to conservative or medical management. Inflammatory pseudotumor (inflammatory myofibroblastic tumor) is a benign, chronic inflammatory disorder of unknown cause that manifests as a solid mesenteric mass, indistinguishable from malignancy. Extrapleural solitary fibrous tumor is a tumor of submesothelial origin that is identical to the solitary fibrous tumor of the pleura. When located in the mesentery or peritoneal cavity, extrapleural solitary fibrous tumor has an imaging pattern that must be differentiated from metastatic disease, soft-tissue sarcomas, and other benign and malignant neoplasms of the mesentery and peritoneum. Knowledge of this group of benign fibrous tumors and tumorlike lesions of the mesentery is important in the preoperative evaluation of a mesenteric mass.
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LEARNING OBJECTIVES FOR TEST 6
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After reading this article and taking the test, the reader will be able to:
- Identify the radiologic and pathologic features of benign tumors and tumor-like lesions of the mesentery.
- Describe the pathologic and radiologic features of mesenteric fibromatosis, sclerosing mesenteritis, and inflammatory pseudotumor.
- Discuss the differential diagnosis and management of patients with mesenteric fibromatosis, sclerosing mesenteritis, and inflammatory pseudotumor.
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Introduction
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Benign fibrous tumors and tumorlike lesions of the mesentery are rare, but they represent an important group of diseases because accurate diagnosis of these lesions is frequently difficult. Furthermore, these lesions may have radiologic and pathologic features similar to those of primary and metastatic malignancies, inflammatory processes from the adjacent bowel or pancreas, and posttraumatic hematomas. Classification and study of benign fibrous tumors and tumorlike lesions of the mesentery is hampered by the lack of standardized nomenclature in the medical literature. The numerous synonyms that exist for mesenteric fibromatosis, sclerosing mesenteritis, inflammatory pseudotumor, and extrapleural solitary fibrous tumor are indicative of their diverse radiologic and pathologic spectrum and, moreover, of the difficulty in making an accurate diagnosis for each one of these conditions.
Although mesenteric fibromatosis, sclerosing mesenteritis, inflammatory pseudotumor, and extrapleural solitary fibrous tumor are distinct diseases, their overlapping radiologic and pathologic features allow them to be grouped together when their anatomic site of origin is a mesenteric structure. Knowledge of this group of uncommon benign diseases is important for accurate diagnosis and appropriate management. This article reviews the clinical, pathologic, and radiologic features of mesenteric fibromatosis, sclerosing mesenteritis, inflammatory pseudotumor, and extrapleural solitary fibrous tumor.
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Mesenteric Fibromatosis
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Clinical Features
Mesenteric fibromatosis, also called intraabdominal fibromatosis or abdominal desmoid, is part of the clinical-pathologic spectrum of deep fibromatoses. The deep fibromatoses encompass a group of benign fibroproliferative processes that are locally aggressive and have the capacity to infiltrate or recur, but not metastasize. The deep fibromatoses are classified by anatomic location because they may arise from intraabdominal sites (mesenteric, pelvic, and retroperitoneal fibromatosis), the deep soft tissues of the abdominal wall (abdominal fibromatosis), and deep within extraabdominal soft tissues (extraabdominal fibromatosis) (1).
The small bowel mesentery is the most common site of origin of intraabdominal fibromatosis. Consequently, the terms mesenteric fibromatosis or mesenteric desmoid tumor are most often applied to this entity. However, other mesenteric structures within the abdomen, such as the omentum, ileocolic mesentery, transverse or sigmoid mesocolon, and ligamentum teres, may be the site of origin for intraabdominal fibromatosis (2).
Mesenteric fibromatosis occurs in a wide age range of patients, 14–75 years of age (mean, 41 years), and has no gender or race predilection (2). In contrast, abdominal fibromatosis occurs most commonly in young women, 20–30 years of age (3). Most cases of mesenteric fibromatosis manifest sporadically. Thirteen percent of patients with mesenteric fibromatosis have familial adenomatous polyposis (FAP), specifically, the Gardner syndrome variant of FAP (2,4).
Prior abdominal surgery is an important risk factor for the development of mesenteric fibromatosis in patients with FAP. Eighty-three percent of patients with FAP and mesenteric fibromatosis have a history of abdominal surgery, most commonly a total colectomy (4). In contrast, only 10% of patients with sporadically occurring mesenteric fibromatosis have previously undergone abdominal surgery (5). In patients with FAP, mesenteric fibromatosis is usually diagnosed within 4 years of their operative procedure.
Two other rare, autosomal dominant hereditary disorders involving unique mutations of the APC (adenomatosis polyposis coli) gene are associated with mesenteric fibromatosis: familial infiltrative fibromatosis and hereditary desmoid disease. Familial infiltrative fibromatosis is characterized by mesenteric fibromatosis and nonpolyposis colorectal cancer (6). Hereditary desmoid disease is an autosomal dominant disorder characterized by multifocal fibromatosis of the paraspinal muscles, breast, occiput, arms, lower ribs, abdominal wall, and mesentery (7).
The presenting clinical signs and symptoms of mesenteric fibromatosis are often related to the small bowel. Patients may complain of abdominal pain or a palpable abdominal mass or come to clinical attention because of complications such as gastrointestinal bleeding, small bowel obstruction, fistula formation, or bowel perforation (2,8).
Pathologic Features
At gross examination, mesenteric fibromatosis is typically a nonencapsulated, well-circumscribed mass (Fig 1a). Occasionally, infiltrative margins are apparent at gross inspection (Fig 2a). Although mesenteric fibromatosis appears well delineated at gross analysis and cross-sectional imaging, its margins are microscopically infiltrating into adjacent structures, particularly the muscularis propria of the small bowel. Cut sections of mesenteric fibromatosis are typically white and may be firm, soft, or myxoid in texture (5).
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Figure 1a. Mesenteric fibromatosis in a gravid 27-year-old woman with FAP who had undergone a total proctocolectomy with J-pouch creation 3 years before. (a) Photograph of the resected specimen shows a smoothly marginated mass with a glistening white and tan cut surface that appears slightly whorled. (b) Computed tomographic (CT) scan obtained after intravenous and oral administration of contrast material shows a well-circumscribed mass immediately adjacent to the J-pouch (arrows). The mass of mesenteric fibromatosis has alternating layers of attenuation. Low-attenuation areas represent myxoid stroma and higher-attenuation areas represent collagenous stroma.
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Figure 1b. Mesenteric fibromatosis in a gravid 27-year-old woman with FAP who had undergone a total proctocolectomy with J-pouch creation 3 years before. (a) Photograph of the resected specimen shows a smoothly marginated mass with a glistening white and tan cut surface that appears slightly whorled. (b) Computed tomographic (CT) scan obtained after intravenous and oral administration of contrast material shows a well-circumscribed mass immediately adjacent to the J-pouch (arrows). The mass of mesenteric fibromatosis has alternating layers of attenuation. Low-attenuation areas represent myxoid stroma and higher-attenuation areas represent collagenous stroma.
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Figure 2a. Mesenteric fibromatosis in an 80-year-old woman who had undergone a right hemicolectomy for adenocarcinoma of the cecum. (a) Photograph of the cut surface of the resected specimen shows an ill-defined, infiltrative white mass adherent to adjacent small bowel segments. (b) CT scan with intravenous contrast material enhancement shows a mixed-attenuation mass in the left lower abdomen that has ill-defined medial borders and well-defined borders that contact the adjacent small bowel.
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Figure 2b. Mesenteric fibromatosis in an 80-year-old woman who had undergone a right hemicolectomy for adenocarcinoma of the cecum. (a) Photograph of the cut surface of the resected specimen shows an ill-defined, infiltrative white mass adherent to adjacent small bowel segments. (b) CT scan with intravenous contrast material enhancement shows a mixed-attenuation mass in the left lower abdomen that has ill-defined medial borders and well-defined borders that contact the adjacent small bowel.
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At microscopic analysis, mesenteric fibromatosis is composed of fibroblasts in an uninflamed, abundant collagenous stroma (Fig 3). The fibroblasts are elongated, spindle-shaped cells with regular uniform nuclei and scant cytoplasm (1). The stroma of mesenteric fibromatosis may be dense or admixed with myxoid foci. In some tumors, the myxoid stroma predominates. One of the most characteristic features of mesenteric fibromatosis is tentacular insinuation into or through the muscularis propria of the bowel wall (2). This microscopic feature is referred to as melting insinuation (Fig 3). Burke et al (2) identified additional microscopic features that are helpful in establishing the diagnosis of mesenteric fibromatosis: keloidal fiber formation, thick-walled small arteries, thin-walled veins, and perivascular microhemorrhages (Fig 3).
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Figure 3a. Histologic features of mesenteric fibromatosis. (a) Photomicrograph (original magnification, x10; hematoxylineosin [H-E] stain) shows fibroblasts in a collagenous stroma. Perivascular microhemorrhages (arrows) are present throughout. (b) Photomicrograph (original magnification, x10; H-E stain) shows numerous thin-walled veins (arrow). (c) Photomicrograph (original magnification, x10; H-E stain) shows keloidal fibers. (d) Photomicrograph (original magnification, x4; H-E stain) shows the lesion (arrows) "melting" into the muscularis propria.
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Figure 3b. Histologic features of mesenteric fibromatosis. (a) Photomicrograph (original magnification, x10; hematoxylineosin [H-E] stain) shows fibroblasts in a collagenous stroma. Perivascular microhemorrhages (arrows) are present throughout. (b) Photomicrograph (original magnification, x10; H-E stain) shows numerous thin-walled veins (arrow). (c) Photomicrograph (original magnification, x10; H-E stain) shows keloidal fibers. (d) Photomicrograph (original magnification, x4; H-E stain) shows the lesion (arrows) "melting" into the muscularis propria.
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Figure 3c. Histologic features of mesenteric fibromatosis. (a) Photomicrograph (original magnification, x10; hematoxylineosin [H-E] stain) shows fibroblasts in a collagenous stroma. Perivascular microhemorrhages (arrows) are present throughout. (b) Photomicrograph (original magnification, x10; H-E stain) shows numerous thin-walled veins (arrow). (c) Photomicrograph (original magnification, x10; H-E stain) shows keloidal fibers. (d) Photomicrograph (original magnification, x4; H-E stain) shows the lesion (arrows) "melting" into the muscularis propria.
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Figure 3d. Histologic features of mesenteric fibromatosis. (a) Photomicrograph (original magnification, x10; hematoxylineosin [H-E] stain) shows fibroblasts in a collagenous stroma. Perivascular microhemorrhages (arrows) are present throughout. (b) Photomicrograph (original magnification, x10; H-E stain) shows numerous thin-walled veins (arrow). (c) Photomicrograph (original magnification, x10; H-E stain) shows keloidal fibers. (d) Photomicrograph (original magnification, x4; H-E stain) shows the lesion (arrows) "melting" into the muscularis propria.
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Mesenteric fibromatosis may be confused radiologically and histologically with a gastrointestinal stromal tumor (GIST). GISTs within the mesentery occur as an extension of a small bowel GIST, metastatic disease, or, in rare cases, a primary mesenteric GIST (9). At microscopic analysis, GISTs may be composed of spindle cells that closely resemble those of mesenteric fibromatosis, but GIST spindle cells are much more cellular and without abundant collagenous stroma. The immunohistochemical profile of mesenteric fibromatosis—in addition to its light microscopic features of melting insinuation, keloidal fiber formation, thin-walled veins, thick-walled small arteries, and perivascular microhemorrhages—is helpful for differentiating it from a GIST. Mesenteric fibromatosis is typically negative for cell markers CD34 and CD117, in contrast to GISTs, which are almost universally positive for CD117 and often positive for CD34.
Radiologic Features
Abdominal radiography may show evidence of mass effect or a prominent soft-tissue mass centered within the abdomen in patients with mesenteric fibromatosis (Figs 4, 5) (10). Displacement of small bowel segments is common. Occasionally, colonic segments may be involved, specifically the transverse colon if the site of origin is the transverse mesocolon (Fig 5).
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Figure 4a. Mesenteric fibromatosis in a 48-year-old man who complained of abdominal fullness. (a) Abdominal radiograph obtained with the patient supine shows a large, oval, soft-tissue mass (arrows) in the upper abdomen that displaces the transverse colon inferiorly. (b) CT scan with intravenous and oral contrast material enhancement shows a well-defined, oval, nonenhancing, hypoattenuating mass in the region of the transverse mesocolon.
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Figure 4b. Mesenteric fibromatosis in a 48-year-old man who complained of abdominal fullness. (a) Abdominal radiograph obtained with the patient supine shows a large, oval, soft-tissue mass (arrows) in the upper abdomen that displaces the transverse colon inferiorly. (b) CT scan with intravenous and oral contrast material enhancement shows a well-defined, oval, nonenhancing, hypoattenuating mass in the region of the transverse mesocolon.
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Figure 5a. Mesenteric fibromatosis in a 37-year-old woman who complained of abdominal pain and a palpable abdominal mass. (a) Image from an air contrast barium enema study shows a smoothly marginated mass (arrows) on the inferior surface of the mid-transverse colon. (b) CT scan with intravenous and oral contrast material enhancement shows an oval, partially enhancing mass (arrows) involving the wall of the transverse colon. The epicenter of the mass is in the small bowel mesentery.
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Figure 5b. Mesenteric fibromatosis in a 37-year-old woman who complained of abdominal pain and a palpable abdominal mass. (a) Image from an air contrast barium enema study shows a smoothly marginated mass (arrows) on the inferior surface of the mid-transverse colon. (b) CT scan with intravenous and oral contrast material enhancement shows an oval, partially enhancing mass (arrows) involving the wall of the transverse colon. The epicenter of the mass is in the small bowel mesentery.
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The histologic infiltration of mesenteric fibromatosis into adjacent bowel wall may result in partial or complete small bowel obstruction (Fig 6), fistula formation, or bowel perforation. Mucosal ulceration may also occur as mesenteric fibromatosis infiltrates through the mesentery and bowel wall (Fig 7). It has been suggested that mucosal ulceration is a manifestation of ischemia that results from compromised mesenteric vasculature in patients with mesenteric fibromatosis (11). We have observed several cases of mesenteric fibromatosis in which the lesion completely encircled the bowel. The most common result is luminal narrowing. However, we have also identified a pattern of luminal dilatation with mucosal ulceration that mimics lymphoma (Fig 7a ). In such cases, barium or enteroclysis evaluation of the small intestine may reveal distorted, thickened, or effaced small bowel folds with mucosal irregularity and ulceration.
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Figure 6a. Mesenteric fibromatosis in a 69-year-old man with nausea, vomiting, and abdominal distention. (a) Image from a barium examination of the small bowel shows a partial obstruction in the small intestine. The transition point (arrow) for the obstruction is in the right midabdomen at the site of the mass effect. The small bowel is draped around and displaced by a rounded mass. (b) Photograph of the unopened, resected specimen show a well-circumscribed mass of mesenteric fibromatosis (*) and the transition point for the small bowel obstruction (arrow). The small bowel is adherent to the mass of mesenteric fibromatosis.
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Figure 6b. Mesenteric fibromatosis in a 69-year-old man with nausea, vomiting, and abdominal distention. (a) Image from a barium examination of the small bowel shows a partial obstruction in the small intestine. The transition point (arrow) for the obstruction is in the right midabdomen at the site of the mass effect. The small bowel is draped around and displaced by a rounded mass. (b) Photograph of the unopened, resected specimen show a well-circumscribed mass of mesenteric fibromatosis (*) and the transition point for the small bowel obstruction (arrow). The small bowel is adherent to the mass of mesenteric fibromatosis.
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Figure 7a. Mesenteric fibromatosis in a 46-year-old man who complained of a left-sided abdominal mass and who had guaiac-positive stools and anemia. (a) Image from a small bowel barium examination shows mass effect in the left lower quadrant and a displaced segment of small intestine (arrows), which has irregularly thickened folds and distorted luminal caliber. Mucosal ulceration is also present. (b) Photograph of the opened, resected specimen shows the mucosal surface of the small bowel with a large defect (*) from the adjacent mass of mesenteric fibromatosis.
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Figure 7b. Mesenteric fibromatosis in a 46-year-old man who complained of a left-sided abdominal mass and who had guaiac-positive stools and anemia. (a) Image from a small bowel barium examination shows mass effect in the left lower quadrant and a displaced segment of small intestine (arrows), which has irregularly thickened folds and distorted luminal caliber. Mucosal ulceration is also present. (b) Photograph of the opened, resected specimen shows the mucosal surface of the small bowel with a large defect (*) from the adjacent mass of mesenteric fibromatosis.
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Although sonography is not typically performed as a primary imaging modality to assess the mesentery, mesenteric masses may be discovered incidentally when patients are being evaluated for complaints of abdominal discomfort or pain. The sonographic appearance of mesenteric fibromatosis is a solid, well-circumscribed mass of variable echotexture and homogeneity (Fig 8) (10,12).
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Figure 8a. Mesenteric fibromatosis in a 42-year-old woman who complained of abdominal distention and pain. (a) Transverse sonogram of the right abdomen shows a well-defined, mixed-echotexture mass. (b) CT scan with intravenous and oral contrast material enhancement shows a well-defined, 18-cm mass centered in the small bowel mesentery. The mass has homogeneous attenuation with the exception of focal low attenuation along its anterior aspect.
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Figure 8b. Mesenteric fibromatosis in a 42-year-old woman who complained of abdominal distention and pain. (a) Transverse sonogram of the right abdomen shows a well-defined, mixed-echotexture mass. (b) CT scan with intravenous and oral contrast material enhancement shows a well-defined, 18-cm mass centered in the small bowel mesentery. The mass has homogeneous attenuation with the exception of focal low attenuation along its anterior aspect.
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CT and magnetic resonance (MR) imaging are the preferred imaging modalities for preoperative assessment of mesenteric masses. The multiplanar capabilities of multidetector CT and MR imaging are ideal for determining lesion size and extent, as well as the degree of invasion into local structures. The CT and MR imaging appearances of mesenteric fibromatosis are directly related to its underlying histologic characteristics and vascularity (13–15). Lesions with a highly collagenous stroma usually have homogeneous, soft-tissue attenuation on CT scans (Fig 9). Those with myxoid stroma appear hypoattenuating. Some lesions have both collagenous and myxoid stroma and may appear striated or whorled because of the alternating collagenous and myxoid areas (Fig 1b) (16). Mesenteric fibromatosis has been reported to show little contrast material enhancement on CT scans (14,16,17). In our case material, we have seen variable contrast enhancement patterns, from mild homogeneous enhancement to heterogeneous enhancement (Fig 5b). Predominantly myxoid lesions typically remain hypoattenuating and do not enhance with intravenous contrast material (Fig 10).
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Figure 9a. Mesenteric fibromatosis in a 55-year-old woman with a history of hysterectomy and ureteral reimplantation who presented with signs and symptoms of small bowel obstruction. Contiguous CT scans with intravenous and oral contrast material enhancement show a homogeneously attenuating soft-tissue mass (*) in the small bowel mesentery. The mass has ill-defined borders (arrow in a) along its right margin in contact with adjacent small bowel segments.
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Figure 9b. Mesenteric fibromatosis in a 55-year-old woman with a history of hysterectomy and ureteral reimplantation who presented with signs and symptoms of small bowel obstruction. Contiguous CT scans with intravenous and oral contrast material enhancement show a homogeneously attenuating soft-tissue mass (*) in the small bowel mesentery. The mass has ill-defined borders (arrow in a) along its right margin in contact with adjacent small bowel segments.
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Figure 10a. Mesenteric fibromatosis with myxoid stroma in a 46-year-old woman who complained of left upper quadrant and shoulder pain. CT scans (a obtained cephalad to b) with intravenous and oral contrast material enhancement show a hypoattenuating, 18-cm mass (*) in the left upper quadrant that arises from the greater omentum. Gallstones are an incidental finding.
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Figure 10b. Mesenteric fibromatosis with myxoid stroma in a 46-year-old woman who complained of left upper quadrant and shoulder pain. CT scans (a obtained cephalad to b) with intravenous and oral contrast material enhancement show a hypoattenuating, 18-cm mass (*) in the left upper quadrant that arises from the greater omentum. Gallstones are an incidental finding.
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The MR imaging manifestations of mesenteric fibromatosis, similar to the CT findings, reflect the relative abundance of collagen or myxoid stroma within the lesion. Most lesions are low or intermediate signal intensity on T1-weighted images and have heterogeneously intermediate or high signal intensity on T2-weighted images (18) (Figs 11, 12). Myxoid stromal elements contribute to the high signal intensity, and the relative amount of hyperintensity on T2-weighted images reflects the degree of cellularity and myxoid stroma in the lesion. The intravenous contrast material enhancement pattern of mesenteric fibromatosis on MR images is variable, similar to the pattern observed at CT. Some lesions that do not enhance with iodinated contrast material on CT scans have been shown to enhance with intravenous gadolinium on MR images (Fig 12) (19).
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Figure 11a. Mesenteric fibromatosis in a 31-year-old man who complained of epigastric fullness and early satiety. (a) T1-weighted MR image shows a well-defined, low-signal-intensity mass within the small bowel mesentery. (b, c) On T2-weighted images obtained without (b) and with (c) fat suppression, the mass has heterogeneously high signal intensity. (d) T1-weighted fat-suppressed MR image obtained with intravenous gadolinium shows heterogeneous enhancement of the mass.
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Figure 11b. Mesenteric fibromatosis in a 31-year-old man who complained of epigastric fullness and early satiety. (a) T1-weighted MR image shows a well-defined, low-signal-intensity mass within the small bowel mesentery. (b, c) On T2-weighted images obtained without (b) and with (c) fat suppression, the mass has heterogeneously high signal intensity. (d) T1-weighted fat-suppressed MR image obtained with intravenous gadolinium shows heterogeneous enhancement of the mass.
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Figure 11c. Mesenteric fibromatosis in a 31-year-old man who complained of epigastric fullness and early satiety. (a) T1-weighted MR image shows a well-defined, low-signal-intensity mass within the small bowel mesentery. (b, c) On T2-weighted images obtained without (b) and with (c) fat suppression, the mass has heterogeneously high signal intensity. (d) T1-weighted fat-suppressed MR image obtained with intravenous gadolinium shows heterogeneous enhancement of the mass.
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Figure 11d. Mesenteric fibromatosis in a 31-year-old man who complained of epigastric fullness and early satiety. (a) T1-weighted MR image shows a well-defined, low-signal-intensity mass within the small bowel mesentery. (b, c) On T2-weighted images obtained without (b) and with (c) fat suppression, the mass has heterogeneously high signal intensity. (d) T1-weighted fat-suppressed MR image obtained with intravenous gadolinium shows heterogeneous enhancement of the mass.
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Figure 12a. Mesenteric fibromatosis in a 57-year-old man with long-standing Crohn disease and a history of prior right hemicolectomy who presented with abdominal pain. (a) CT scan with intravenous contrast material enhancement shows an ill-defined mass (arrow) in the small bowel mesentery. Multiple small mesenteric lymph nodes are present. (b–d) MR images show that the mass has low signal intensity with a fast spoiled gradient-echo nonenhanced pulse sequence (arrow in b), has heterogeneously high signal intensity with T2 weighting (arrow in c), and enhances with a fat-saturated, fast spoiled gradient-echo pulse sequence and intravenous gadolinium (arrow in d).
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Figure 12b. Mesenteric fibromatosis in a 57-year-old man with long-standing Crohn disease and a history of prior right hemicolectomy who presented with abdominal pain. (a) CT scan with intravenous contrast material enhancement shows an ill-defined mass (arrow) in the small bowel mesentery. Multiple small mesenteric lymph nodes are present. (b–d) MR images show that the mass has low signal intensity with a fast spoiled gradient-echo nonenhanced pulse sequence (arrow in b), has heterogeneously high signal intensity with T2 weighting (arrow in c), and enhances with a fat-saturated, fast spoiled gradient-echo pulse sequence and intravenous gadolinium (arrow in d).
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Figure 12c. Mesenteric fibromatosis in a 57-year-old man with long-standing Crohn disease and a history of prior right hemicolectomy who presented with abdominal pain. (a) CT scan with intravenous contrast material enhancement shows an ill-defined mass (arrow) in the small bowel mesentery. Multiple small mesenteric lymph nodes are present. (b–d) MR images show that the mass has low signal intensity with a fast spoiled gradient-echo nonenhanced pulse sequence (arrow in b), has heterogeneously high signal intensity with T2 weighting (arrow in c), and enhances with a fat-saturated, fast spoiled gradient-echo pulse sequence and intravenous gadolinium (arrow in d).
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Figure 12d. Mesenteric fibromatosis in a 57-year-old man with long-standing Crohn disease and a history of prior right hemicolectomy who presented with abdominal pain. (a) CT scan with intravenous contrast material enhancement shows an ill-defined mass (arrow) in the small bowel mesentery. Multiple small mesenteric lymph nodes are present. (b–d) MR images show that the mass has low signal intensity with a fast spoiled gradient-echo nonenhanced pulse sequence (arrow in b), has heterogeneously high signal intensity with T2 weighting (arrow in c), and enhances with a fat-saturated, fast spoiled gradient-echo pulse sequence and intravenous gadolinium (arrow in d).
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In patients with FAP and mesenteric fibromatosis, the latter more commonly manifests with several lesions, which, at the time of diagnosis, tend to be smaller compared with the lesions seen in patients with sporadically occurring mesenteric fibromatosis (17). In patients with FAP, mesenteric fibromatosis may occur in conjunction with fibromatosis in the abdominal wall (abdominal fibromatosis). In the majority of cases, the CT and MR imaging appearances of mesenteric fibromatosis associated with FAP are similar. Because mesenteric fibromatosis is frequently preceded by surgery in patients with FAP, the fibromatosis may occur in or around anastomotic or surgical sites in these patients (Fig 1b). In rare cases, a diffuse form of fibromatosis that involves the mesentery, pelvis, and retroperitoneum may be seen in patients with FAP (Fig 13). Pelvic and retroperitoneal fibromatosis is most commonly an extension of mesenteric fibromatosis with diffusely infiltrating margins.
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Figure 13a. Mesenteric, retroperitoneal, and pelvic fibromatosis in a 28-year-old woman with FAP who had undergone a subtotal colectomy. CT scans with intravenous contrast material enhancement (obtained at successively caudal levels) show an infiltrating mass in the mesentery and retroperitoneum (arrows). The mass encases the right ureter, in which a stent had been placed (bright spot in c) and infiltrates adjacent small bowel segments. Right hydronephrosis is seen.
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Figure 13b. Mesenteric, retroperitoneal, and pelvic fibromatosis in a 28-year-old woman with FAP who had undergone a subtotal colectomy. CT scans with intravenous contrast material enhancement (obtained at successively caudal levels) show an infiltrating mass in the mesentery and retroperitoneum (arrows). The mass encases the right ureter, in which a stent had been placed (bright spot in c) and infiltrates adjacent small bowel segments. Right hydronephrosis is seen.
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Figure 13c. Mesenteric, retroperitoneal, and pelvic fibromatosis in a 28-year-old woman with FAP who had undergone a subtotal colectomy. CT scans with intravenous contrast material enhancement (obtained at successively caudal levels) show an infiltrating mass in the mesentery and retroperitoneum (arrows). The mass encases the right ureter, in which a stent had been placed (bright spot in c) and infiltrates adjacent small bowel segments. Right hydronephrosis is seen.
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Differential Diagnosis
On the basis of imaging findings alone, mesenteric fibromatosis is difficult to differentiate from malignant neoplasms of the mesentery, such as lymphoma, metastatic disease, and soft-tissue sarcoma. Mesenteric fibromatosis, as well as inflammatory pseudotumor and extrapleural solitary fibrous tumor, may closely resemble the CT and MR imaging appearances of lymphoma when the lesions manifest with well-defined margins, homogeneous attenuation, and involvement of adjacent small bowel segments.
GISTs of the small bowel may have an extensive mesenteric component or may occur primarily in the mesentery. Therefore, GISTs should be considered in the differential diagnosis of mesenteric fibromatosis, inflammatory pseudotumor, and extrapleural solitary fibrous tumor. Large GISTs typically contain areas of hemorrhage and necrosis, which manifest as focal areas of hypoattenuation (20). Although focal necrosis is not a typical feature of mesenteric fibromatosis, focal areas of hypoattenuating myxoid stroma may be confused for necrosis on cross-sectional images.
Soft-tissue sarcomas that arise in the mesentery or retroperitoneum such as liposarcoma, fibrosarcoma, leiomyosarcoma, and undifferentiated pleomorphic high-grade sarcoma (also known as malignant fibrous histiocytoma) should be considered in the differential diagnosis of solid mesenteric masses in adults.
Treatment and Prognosis
The management of patients with mesenteric fibromatosis is controversial. Not only does mesenteric fibromatosis have a proclivity for local recurrence following resection, but the location of the primary disease in the bowel mesentery predisposes patients to developing complications such as small bowel obstruction and fistula formation. Some authors recommend wide surgical excision, whereas others recommend less radical surgery or medical therapy with antiestrogens or cytotoxic chemotherapy (21–25). Surgery for patients with sporadically occurring mesenteric fibromatosis is frequently curative, but it may be associated with significant morbidity (8). Although in some cases, reexcision and postoperative irradiation, endocrine therapy, or chemotherapy may be necessary, patients with sporadically occurring mesenteric fibromatosis rarely die of fibromatosis (1). In contrast, patients with FAP and mesenteric fibromatosis have a significantly higher rate of recurrence and disease that is more difficult to control. Consequently, for these patients, many authors suggest nonsurgical treatment and reserve surgery to treat complications such as bowel obstruction (4,26).
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Sclerosing Mesenteritis
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Clinical Features
Sclerosing mesenteritis is an unusual, idiopathic disorder characterized by tumorlike masses in the mesentery that are composed of chronic, nonspecific inflammation, fat necrosis, and fibrosis. Sclerosing mesenteritis involves the small bowel mesentery in most cases, but it can also affect the colonic mesocolon (27,28). In the majority of cases, the mesentery becomes thickened and shortened. Fixation and kinking of the bowel may occur. There are many synonyms in the literature for sclerosing mesenteritis: mesenteric panniculitis, retractile mesenteritis, mesenteric lipodystrophy, lipogranuloma of the mesentery, sclerosing lipogranulomatosis, primary liposclerosis of the mesentery, and multifocal subperitoneal sclerosis (5). The variable nomenclature for sclerosing mesenteritis results from the varying descriptions of histologic features that may be observed in this apparently single clinical-pathologic entity (29).
The average age of patients at presentation for sclerosing mesenteritis is 60 years, and the condition occurs twice as often in men than women (29). Abdominal pain or a palpable abdominal mass is the most common clinical manifestation (29,30). Other signs and symptoms include weight loss, abdominal distention, vomiting, diarrhea, constipation, and fever of unknown origin. In rare cases, sclerosing mesenteritis may be discovered incidentally.
Pathologic Features
At gross examination, sclerosing mesenteritis may be solitary or multifocal within the mesentery. The lesion has a firm, gritty consistency when sectioned (5,29,31). It may be well demarcated or diffusely infiltrating. The diffusely infiltrating form manifests as thickening of the mesentery.
At histologic analysis, sclerosing mesenteritis has many features, including sclerosing fibrosis, fat necrosis with lipid-laden macrophages, chronic inflammation with germinal centers, and focal calcification (Fig 14) (29,32). One or more of these features may predominate during the course of the disease. Accordingly, early in the course of the disease, sclerosing mesenteritis has a loose myxomatous appearance. Later phases are characterized by marked inflammation, and finally dense sclerosis develops. These distinct phases may coexist within one lesion (Fig 14d).
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Figure 14a. Histologic features of sclerosing mesenteritis. (a) Photomicrograph (original magnification, x10; H-E stain) shows fat necrosis, sclerosing fibrosis (*), and inflammatory cells (arrow). (b) Photomicrograph (original magnification, x16; H-E stain) shows the inflammatory infiltrate (arrowheads) extending to the edge of the muscularis propria. The inflammatory process does not extend into the muscularis propria. (c) Photomicrograph (original magnification, x40; H-E stain) shows dense sclerosis, typical of sclerosing mesenteritis, with an accompanying inflammatory infiltrate. (d) Photomicrograph (original magnification, x16; H-E stain) shows the dense sclerosis, which abuts the loose myxomatous stroma (*) and forms a pseudocapsule.
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Figure 14b. Histologic features of sclerosing mesenteritis. (a) Photomicrograph (original magnification, x10; H-E stain) shows fat necrosis, sclerosing fibrosis (*), and inflammatory cells (arrow). (b) Photomicrograph (original magnification, x16; H-E stain) shows the inflammatory infiltrate (arrowheads) extending to the edge of the muscularis propria. The inflammatory process does not extend into the muscularis propria. (c) Photomicrograph (original magnification, x40; H-E stain) shows dense sclerosis, typical of sclerosing mesenteritis, with an accompanying inflammatory infiltrate. (d) Photomicrograph (original magnification, x16; H-E stain) shows the dense sclerosis, which abuts the loose myxomatous stroma (*) and forms a pseudocapsule.
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Figure 14c. Histologic features of sclerosing mesenteritis. (a) Photomicrograph (original magnification, x10; H-E stain) shows fat necrosis, sclerosing fibrosis (*), and inflammatory cells (arrow). (b) Photomicrograph (original magnification, x16; H-E stain) shows the inflammatory infiltrate (arrowheads) extending to the edge of the muscularis propria. The inflammatory process does not extend into the muscularis propria. (c) Photomicrograph (original magnification, x40; H-E stain) shows dense sclerosis, typical of sclerosing mesenteritis, with an accompanying inflammatory infiltrate. (d) Photomicrograph (original magnification, x16; H-E stain) shows the dense sclerosis, which abuts the loose myxomatous stroma (*) and forms a pseudocapsule.
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Figure 14d. Histologic features of sclerosing mesenteritis. (a) Photomicrograph (original magnification, x10; H-E stain) shows fat necrosis, sclerosing fibrosis (*), and inflammatory cells (arrow). (b) Photomicrograph (original magnification, x16; H-E stain) shows the inflammatory infiltrate (arrowheads) extending to the edge of the muscularis propria. The inflammatory process does not extend into the muscularis propria. (c) Photomicrograph (original magnification, x40; H-E stain) shows dense sclerosis, typical of sclerosing mesenteritis, with an accompanying inflammatory infiltrate. (d) Photomicrograph (original magnification, x16; H-E stain) shows the dense sclerosis, which abuts the loose myxomatous stroma (*) and forms a pseudocapsule.
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One of the most important histologic features that distinguishes sclerosing mesenteritis from mesenteric fibromatosis is that it does not penetrate the muscularis propria of the adjacent bowel wall. Sclerosing mesenteritis stops abruptly at the bowel wall (Fig 14b) (29). In contrast, mesenteric fibromatosis infiltrates or shows "melting insinuation" into the muscularis propria of the bowel wall (Fig 3).
Radiologic Features
Sclerosing mesenteritis affects the small bowel by retraction and shortening of the mesentery rather than by direct extension or invasion. The result of mesenteric retraction and shortening is kinking or fixation of the small bowel (Fig 15). Partial or complete obstruction of the small intestines may occur. As a result, patients may present with radiographic manifestations of small bowel obstruction: intestinal dilatation, fluid levels, and fluid-filled bowel. Reactive mural thickening may also occur, which manifests radiologically as irregular fold thickening at barium or enteroclysis evaluation of the small bowel (Fig 15a ) (33).
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Figure 15a. Sclerosing mesenteritis in a 73-year-old man with abdominal pain, nausea, vomiting, and diarrhea. (a) Image from a small bowel barium examination shows tethered segments of small intestine that are fixed in the midabdomen. There is mild dilatation of a segment of small bowel and irregular fold thickening (arrowheads). (b) CT scan with intravenous and oral contrast material enhancement shows a partially calcified mass at the root of the small bowel mesentery. Fibrous strands radiate from the mass and fix portions of the small bowel. (c) Photograph of the cut surface of the resected specimen shows the multifocal firm, yellow mass (arrows) in the root of the small bowel mesentery. The mesenteric fat and adjacent bowel are retracted.
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Figure 15b. Sclerosing mesenteritis in a 73-year-old man with abdominal pain, nausea, vomiting, and diarrhea. (a) Image from a small bowel barium examination shows tethered segments of small intestine that are fixed in the midabdomen. There is mild dilatation of a segment of small bowel and irregular fold thickening (arrowheads). (b) CT scan with intravenous and oral contrast material enhancement shows a partially calcified mass at the root of the small bowel mesentery. Fibrous strands radiate from the mass and fix portions of the small bowel. (c) Photograph of the cut surface of the resected specimen shows the multifocal firm, yellow mass (arrows) in the root of the small bowel mesentery. The mesenteric fat and adjacent bowel are retracted.
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Figure 15c. Sclerosing mesenteritis in a 73-year-old man with abdominal pain, nausea, vomiting, and diarrhea. (a) Image from a small bowel barium examination shows tethered segments of small intestine that are fixed in the midabdomen. There is mild dilatation of a segment of small bowel and irregular fold thickening (arrowheads). (b) CT scan with intravenous and oral contrast material enhancement shows a partially calcified mass at the root of the small bowel mesentery. Fibrous strands radiate from the mass and fix portions of the small bowel. (c) Photograph of the cut surface of the resected specimen shows the multifocal firm, yellow mass (arrows) in the root of the small bowel mesentery. The mesenteric fat and adjacent bowel are retracted.
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On CT scans, sclerosing mesenteritis manifests as a well-demarcated or ill-defined mesenteric mass with soft-tissue or mixed fat and soft-tissue attenuation (Fig 16) (30,34). The process may envelop the mesenteric vessels, with preservation of a fatty collar around the vessels, a finding that has been referred to as the fat ring sign (30,35). Punctate or coarse calcifications may be present within the lesion (Figs 16, 17). Radiating strands of fibrosis may be evident as linear soft-tissue spicules emanating from the mesenteric mass (Fig 16).
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Figure 16a. Sclerosing mesenteritis in a 70-year-old man who complained of abdominal pain and distention. (a, b) CT scans (a obtained cephalad to b) with intravenous contrast material enhancement show a partial small bowel obstruction and a fixed segment of small intestine in the midabdomen that radiates around a spiculated, partially calcified mass in the small bowel mesentery (arrow). Radiating bands of fibrosis extend from the mass to the small bowel. (c) Intraoperative photograph shows nodules (straight arrow) and thickening (curved arrow) at the root of the small bowel mesentery.
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Figure 16b. Sclerosing mesenteritis in a 70-year-old man who complained of abdominal pain and distention. (a, b) CT scans (a obtained cephalad to b) with intravenous contrast material enhancement show a partial small bowel obstruction and a fixed segment of small intestine in the midabdomen that radiates around a spiculated, partially calcified mass in the small bowel mesentery (arrow). Radiating bands of fibrosis extend from the mass to the small bowel. (c) Intraoperative photograph shows nodules (straight arrow) and thickening (curved arrow) at the root of the small bowel mesentery.
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Figure 16c. Sclerosing mesenteritis in a 70-year-old man who complained of abdominal pain and distention. (a, b) CT scans (a obtained cephalad to b) with intravenous contrast material enhancement show a partial small bowel obstruction and a fixed segment of small intestine in the midabdomen that radiates around a spiculated, partially calcified mass in the small bowel mesentery (arrow). Radiating bands of fibrosis extend from the mass to the small bowel. (c) Intraoperative photograph shows nodules (straight arrow) and thickening (curved arrow) at the root of the small bowel mesentery.
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Abstract
LEARNING OBJECTIVES FOR TEST...
