AJR 2005; 184:1128-1135
© American Roentgen Ray Society
MRI Features of Mesenteric Desmoid Tumors in Familial Adenomatous Polyposis
Louisa Azizi,
Marie Balu,
Ahcène Belkacem,
Maité Lewin,
Jean-Michel Tubiana and
Lionel Arrivé
Department of Radiology, Hôpital Saint-Antoine, 184 rue du faubourg
Saint-Antoine, Paris 75012, France.
Received June 17, 2004;
accepted after revision September 16, 2004.
Address correspondence to L. Azizi
(louisa.azizi{at}sat.ap-hop-paris.fr).
Introduction
Familial adenomatous polyposis (FAP) is an autosomal dominant
disease caused by a germline abnormality of the adenomatous polyposis coli
gene on the long arm of chromosome 5
[1]. FAP is characterized by
the presence of hundreds or thousands of colorectal adenomas. Malignant
transformation is inevitable and prophylactic colectomy is usually
recommended.
Desmoid tumors occur in 9-18% of patients with FAP. They arise within the
musculoaponeurotic structures of the abdominal wall, particularly near
surgical scars or within the abdomen (usually within the small bowel
mesentery) [2]. Desmoid tumors
arise from aggressive fibroblastic proliferation of locally invasive,
differentiated fibrous tissue and are one of the most important and intriguing
extracolonic manifestations of FAP. Desmoid tumors behave unpredictably, some
growing rapidly, others regressing spontaneously
[3].
The infiltrative nature of mesenteric desmoid tumors can lead to bowel loop
or ureter obstruction or damage to blood vessels, causing life-threatening
complications.
Mesenteric desmoid tumors are a major cause of morbidity and mortality in
patients with FAP, who have undergone prophylactic colectomy
[4]. The therapeutic management
of desmoid tumors is controversial. Numerous treatments have been tried, but
none has proven effective. Nonsteroidal antiinflammatory drugs and
antiestrogen agents are the most common form of medical treatment. Radiation
therapy is effective on abdominal wall desmoid tumors, but its value is
uncertain in the treatment of mesenteric desmoids
[5]. Most authors recommend
avoiding surgery because it carries a high mortality rate and often requires
sacrifice of considerable lengths of small bowel. Even if excision is
successful, recurrence occurs in up to 88% of cases
[6] and so is not recommended
unless the desmoid tumor becomes symptomatic
[7].
In this pictorial essay, we review the MRI features of mesenteric desmoid
tumors, focusing on morphologic characteristics, signal intensity,
enhancement, and local complications.
Morphologic Characteristics
The excellent soft-tissue contrast of MRI and its multiplanar capabilities
offer accurate tumor delineation and precise appreciation of infiltration of
adjacent structures. Intraabdominal desmoid tumors may appear mass-like or
infiltrative.
When masslike, desmoid tumors are usually large and well-defined masses,
measuring up to 25 cm at diagnosis (Fig.
1A), and they may compress or displace adjacent structures. When
infiltrative, a desmoid tumor appears as an ill-defined whorled soft-tissue
thickening within the mesenteric fat (Figs.
2A,
2B,
2C and
3), usually causing angulation
or spiculation of adjacent bowel loops (Figs.
4A, and
4B). Both masslike and
infiltrative desmoid tumors can be present in the same patient (Figs.
5A,
5B,
5C,
5D,
5E, and
5F).
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Fig. 1A. —Bulky mesenteric desmoid tumor in 51-year-old man. Axial
T2-weighted spin-echo MR image (TR/TE, 4,820/122) shows mixed-signal-intensity
masslike desmoid tumor that contains central areas of high signal
intensity.
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Fig. 2A. —Infiltrative mesenteric desmoid tumor in 54-year-old woman.
Axial T2-weighted spin-echo MR image (TR/TE, 4,820/122) (A) and axial
T1-weighted spin-echo MR image (470/13) (B) show ill-defined desmoid
tumor (arrows) with low-signal-intensity strands in high-signal fat
surrounding mesenteric vessels.
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Fig. 2B. —Infiltrative mesenteric desmoid tumor in 54-year-old woman.
Axial T2-weighted spin-echo MR image (TR/TE, 4,820/122) (A) and axial
T1-weighted spin-echo MR image (470/13) (B) show ill-defined desmoid
tumor (arrows) with low-signal-intensity strands in high-signal fat
surrounding mesenteric vessels.
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Fig. 2C. —Infiltrative mesenteric desmoid tumor in 54-year-old woman.
Contrast-enhanced axial T1-weighted spin-echo MR image (470/13) shows no
significant enhancement of desmoid tumor (arrows).
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Fig. 3. —Small infiltrative mesenteric desmoid tumor in 52-year-old
woman. Axial T1-weighted spin-echo MR image (TR/TE, 670/15) shows subtle
infiltrative desmoid tumor (arrows) surrounding superior mesenteric
artery. In such small infiltrative mesenteric desmoid tumor, mass is faintly
visible and it is shown as minimal whorled soft-tissue thickening within
mesenteric fat.
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Fig. 4A. —Extensive infiltrative mesenteric desmoid tumor in
46-year-old man. Axial T1-weighted spin-echo MR image (TR/TE, 470/13) shows
desmoid tumor (arrows) with ill-defined thickening in mesentery
causing tethering of loops of small bowel.
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Fig. 4B. —Extensive infiltrative mesenteric desmoid tumor in
46-year-old man. Coronal true fast imaging with steady-state free precession
MR image (4.5/1.3) shows desmoid tumor (arrows) infiltrating
mesenteric fat.
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Fig. 5A. —Association of masslike and infiltrative desmoid tumors in
28-year-old woman. Axial T2-weighted spin-echo MR image (TR/TE, 4,820/122)
(A) and axial T1-weighted spin-echo MR image (470/13) (B) show
small masslike mesenteric desmoid tumor (arrows) of homogeneous low
signal intensity within thickened mesenteric fat.
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Fig. 5B. —Association of masslike and infiltrative desmoid tumors in
28-year-old woman. Axial T2-weighted spin-echo MR image (TR/TE, 4,820/122)
(A) and axial T1-weighted spin-echo MR image (470/13) (B) show
small masslike mesenteric desmoid tumor (arrows) of homogeneous low
signal intensity within thickened mesenteric fat.
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Fig. 5C. —Association of masslike and infiltrative desmoid tumors in
28-year-old woman. Contrast-enhanced axial fat-saturated T1-weighted image
(640/12) shows homogeneously enhanced mesenteric masslike desmoid tumor
(arrows). In this case, use of fat suppression greatly aided in
detecting contrast enhancement.
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Fig. 5D. —Association of masslike and infiltrative desmoid tumors in
28-year-old woman. Axial T2-weighted spin-echo MR image (4,820/122) (D)
and axial T1-weighted spin-echo MR image (470/13) (E) show ill-defined
infiltrative desmoid tumor of low signal intensity (arrows).
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Fig. 5E. —Association of masslike and infiltrative desmoid tumors in
28-year-old woman. Axial T2-weighted spin-echo MR image (4,820/122) (D)
and axial T1-weighted spin-echo MR image (470/13) (E) show ill-defined
infiltrative desmoid tumor of low signal intensity (arrows).
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Fig. 5F. —Association of masslike and infiltrative desmoid tumors in
28-year-old woman. Contrast-enhanced axial fat-saturated T1-weighted image
(640/12) shows no significant enhancement of infiltrative desmoid tumor
(arrows).
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Abdominal wall desmoid tumors can be associated with mesenteric desmoid
tumors (Fig. 6B). They usually
arise from musculoaponeurotic structures of the abdominal wall, especially the
rectus and internal oblique muscles. Extension into the abdominal cavity
occurs occasionally.
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Fig. 6B. —Association of masslike and infiltrative mesenteric desmoid
tumors in 48-year-old man. Contrast-enhanced axial T1-weighted spin-echo MR
images (TR/TE, 470/13) show one bulky desmoid tumor with heterogeneous
enhancement (white arrows), containing central areas of necrosis, and
one ill-defined desmoid tumor of low signal intensity (black arrows,
A). Note desmoid tumor involving right rectus abdominis
(asterisk, B).
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Signal Intensity and Enhancement Characteristics
The variable MRI signal characteristics of desmoid tumors reflect
differences in their composition, especially their cellularity and fibrous
content. Most desmoid tumors are heterogeneous soft-tissue lesions of
intermediate signal intensity.
They may be hypointense or isointense with respect to muscle on T1-weighted
images (Fig. 1B). They are
usually mixed but predominantly hyperintense (more than muscle but usually
less than fat) on T2-weighted images (Fig.
1A). After the IV injection of contrast material, desmoid tumors
may show homogeneous (Fig.
5C), inhomogeneous (Fig.
1C), or no significant enhancement
(Fig. 5F). A fat-saturated
T1-weighted sequence may be performed to improve the visualization of contrast
enhancement, but it was not routinely used in our series
(Fig. 5C).
Desmoid tumors with high cellularity and abundant collagen can have high
signal intensity on T2-weighted images. The difference in the signal intensity
of T2-weighted images appears to be determined by cellularity rather than
collagen content [8]. Some
authors have found that rapidly growing desmoid tumors have high signal
intensity on T2-weighted images
[9].
Separate lesions in the same patient may have different signal intensities
on T2-weighted images and show different patterns of contrast enhancement
(Figs. 6A and
6B).
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Fig. 6A. —Association of masslike and infiltrative mesenteric desmoid
tumors in 48-year-old man. Contrast-enhanced axial T1-weighted spin-echo MR
images (TR/TE, 470/13) show one bulky desmoid tumor with heterogeneous
enhancement (white arrows), containing central areas of necrosis, and
one ill-defined desmoid tumor of low signal intensity (black arrows,
A). Note desmoid tumor involving right rectus abdominis
(asterisk, B).
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Complications
Desmoid tumors are among the most common causes of death in patients with
FAP who have undergone prophylactic colectomy
[2]. Although histologically
benign, desmoid tumors often show insidious growth and aggressive
characteristics. They have a tendency to recur locally, even after complete
surgical extirpation [7]. In
some cases, desmoid tumors regress spontaneously
(Fig. 6C).
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Fig. 6C. —Association of masslike and infiltrative mesenteric desmoid
tumors in 48-year-old man. Axial T2-weighted spin-echo MR image (4,820/122)
(10-year follow-up MRI, patient received no treatment) shows complete
regression of masslike desmoid tumor. Infiltrative desmoid tumor is still
present with low-signal-intensity whorled thickening of mesenteric fat
(arrows).
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The infiltrative nature of intraabdominal desmoid tumors can result in
life-threatening complications. Hydronephrosis can occur secondary to both
masslike and infiltrative desmoid tumors (Figs.
7A,
7B,
8A, and
8B). Bowel perforation can be
observed in patients with infiltrative desmoid tumors, whereas tumor necrosis
can be observed in patients with masslike desmoid tumors (Figs.
9,
10A,
10B,
11A, and
11B). Other complications
include bowel obstruction and encasement or compression of vascular
structures.
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Fig. 7A. —Bulky mesenteric desmoid tumor in 25-year-old man. H =
hydronephrosis, M = masslike mesenteric desmoid tumor. Axial fat-saturated
T2-weighted spin-echo MR image (TR/TE, 1,720/87) shows masslike mesenteric
desmoid tumor of mixed signal intensity causing left hydronephrosis.
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Fig. 7B. —Bulky mesenteric desmoid tumor in 25-year-old man. H =
hydronephrosis, M = masslike mesenteric desmoid tumor. Axial T1-weighted
spin-echo MR image (470/13) shows masslike desmoid tumor of low homogeneous
signal intensity.
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Fig. 8A. —Association of bulky and infiltrative mesenteric desmoid
tumors in 25-year-old man. Axial T2-weighted spin-echo MR image (TR/TE,
4,820/122) shows left-sided bulky desmoid tumor (arrows) of mixed
signal intensity and right-sided ill-defined desmoid tumor
(arrowheads) with low-signal-intensity strands in
high-signal-intensity fat.
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Fig. 9. —Bulky mesenteric desmoid tumor in 32-year-old man.
Contrast-enhanced sagittal T1-weighted spin-echo MR image (TR/TE, 670/15)
shows bulky desmoid tumor with heterogeneous enhancement containing large
cavity of necrosis represented by fluid-fluid level (arrows).
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Fig. 10A. —Infiltrative pelvic mesenteric desmoid tumor in 26-year-old
man (A at lower level, B at upper level), Contrast-enhanced
fat-saturated T1-weighted images (TR/TE, 640/12) show multiple fistulous
tracts (arrows) complicating an infiltrative pelvic mesenteric
desmoid tumor, which is no more visualized.
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Fig. 10B. —Infiltrative pelvic mesenteric desmoid tumor in 26-year-old
man (A at lower level, B at upper level), Contrast-enhanced
fat-saturated T1-weighted images (TR/TE, 640/12) show multiple fistulous
tracts (arrows) complicating an infiltrative pelvic mesenteric
desmoid tumor, which is no more visualized.
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Fig. 11A. —Pelvic mesenteric desmoid tumor in 21-year-old man.
Contrast-enhanced parasagittal T1-weighted spinecho MR images (TR/TE, 670/15)
shows small abscess (arrow) located within the presacral space.
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Fig. 11B. —Pelvic mesenteric desmoid tumor in 21-year-old man.
Contrast-enhanced sagittal T1-weighted spin-echo MR images (TR/TE, 670/15)
shows multiple areas of necrosis coursing along the presacral space (arrows)
Desmoid tumor itself is no more visualized as a consequence of necrotic
changes.
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Introduction
Morphologic Characteristics
