DOI:10.2214/AJR.07.2230
AJR 2007; 189:W100-W104
© American Roentgen Ray Society
MRI Findings of Uterine Lipoleiomyoma Correlated with Pathologic Findings
Kazuhiro Kitajima1,2,
Yasushi Kaji1,
Kazufumi Imanaka3,
Ryo Sugihara2 and
Kazuro Sugimura2
1 Department of Radiology, Dokkyo Medical University School of Medicine, Mibu,
Japan.
2 Department of Radiology, Kobe University Graduate School of Medicine, Kobe,
Japan.
3 Department of Radiology, Nishi-Kobe Medical Center, Kobe, Japan.
Received November 3, 2006;
accepted after revision March 28, 2007.
Address correspondence to K. Kitajima, 880 Kita-kobayashi, Mibu,
Shimotuka-gun, Tochigi 321-0293, Japan
(kazu10041976{at}yahoo.co.jp).
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Abstract
OBJECTIVE. Our objective was to describe the MRI findings of uterine
lipoleiomyoma and to correlate them with histopathologic findings.
CONCLUSION. Uterine lipoleiomyoma typically presents as a
well-demarcated mass showing hyperintensity with hypointense amorphous bundles
on T1- and T2-weighted images with chemical shift artifacts. The hyperintense
region suppressed on chemical shift fat-suppressed sequences and the
hypointense bundles enhanced by contrast material pathologically correspond to
mature fat tissue and smooth muscle tissue, respectively. Even in an atypical
case with a small volume of fat tissue in the mass, a fat-suppression MRI
sequence is especially useful for the diagnosis.
Keywords: lipoleiomyoma • MRI • myoma • uterine neoplasms
Introduction
Lipoleiomyoma of the uterus is a rare benign uterine tumor suspected
of being a variation of leiomyoma
[1,
2]. Histologically, uterine
lipoleiomyoma consists of smooth muscle cells, mature adipose tissue, and
fibrous tissue in various ratios. To our knowledge, no published compendium
exists of the broad spectrum of MRI findings of this entity except for case
reports. This study describes the MRI appearance of nine patients with uterine
lipoleiomyoma (seven cases showing typical MRI findings noted in previous case
reports and two cases showing atypical MRI findings with a small volume of
fatty tissue) and correlates these imaging findings with the histopathologic
findings.
Materials and Methods
Between 1997 and 2006, nine patients with surgically proven uterine
lipoleiomyoma underwent pelvic MR examinations preoperatively in two
institutions (Nishi-Kobe Medical Center and Kobe University Graduate School of
Medicine). No ethics committee approval was required at these two institutes
because the study was a retrospective review of clinical cases. The nine
patients ranged in age from 47 to 76 years old (mean, 61 years), and seven
patients (78%) were postmenopausal. Clinical presentation was abdominal
pressure in four patients, irregular menstruation in three, dysuria in one,
and anemia in one. Six patients underwent total abdominal hysterectomy with
bilateral salpingo-oophorectomy and three patients underwent simple
hysterectomy. Coexistence with other nonlipomatous leiomyomas was noted in six
patients. We retrospectively reviewed the clinical records and MRI findings of
the nine patients and correlated these MRI findings with histopathologic
findings.
MRI was performed with a 1.5-T superconducting magnet (Magnetom Vision or
Symphony, Siemens Medical Solutions [n = 5 patients]; or Gry-roscan
Intera, Philips Medical Systems [n =4 patients]) using a phased-array
coil. The slice thickness was 4-6 mm, intersection gap was 1 mm, field-of-view
measurements were 24-33 cm, and matrix size was 192 x 256-256 x
512. The number of signal averages was 1 or 2. A conventional spin-echo
technique was used to obtain T1-weighted images (TR range/TE range,
500-650/9-13) and a turbo spin-echo technique (3,500-4,000/91-106) to obtain
T2-weighted images. The echo-train length ranged from 5 to 10. Sagittal and
axial T1- and T2-weighted images were obtained for all patients. The axial
images were obtained on the body axis, not on the uterine axis, in most
patients. Sagittal or axial chemical shift selective (CHESS) T1-weighted
images were obtained for all patients. Immediately after the IV injection of
0.1 mmol/kg of body weight of gadopentetate dimeglumine (Magnevist, Schering),
CHESS T1-weighted images were obtained in four patients. To reduce
peristalsis, 1 mL of butylscopolamine (Buscopan, Boehringer Ingelheim) was
administered intramuscularly before the examination unless
contraindicated.
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Fig. 1A —55-year-old woman with irregular menstruation (typical case).
Sagittal spin-echo T1-weighted MR image (TR/TE, 530/10) shows 55 x 60
mm, well-circumscribed mass in myometrium of corpus uteri as hyperintense with
hypointense bands.
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Fig. 1B —55-year-old woman with irregular menstruation (typical case).
Sagittal turbo spin-echo T2-weighted MR image (3,570/93) shows mass as
hyperintense with hypointense bands and chemical shift artifact along
frequency direction in mass (arrows).
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Fig. 1C —55-year-old woman with irregular menstruation (typical case).
Fat-suppression chemical shift selective sagittal spin-echo T1-weighted MR
image (530/10) shows signal suppression of hyperintense region on T1-weighted
image (A).
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MRI findings were interpreted with only knowledge of the pathologic
diagnosis of uterine lipoleiomyoma; two radiologists attained consensus
regarding the appearance of the lesion, including the size, location, growth
pattern, signal intensity, chemical shift artifact, and the presence of fat
and hemorrhage. The signal intensity of the lesion was rated on both T1- and
T2-weighted images as low intensity, isointensity, or high intensity relative
to the signal intensity of the myometrium. These radiologic findings were
grossly and micropathologically correlated with pathologic findings.
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Fig. 2A —65-year-old woman with abdominal pressure (typical case).
Axial spin-echo T1-weighted MR image (TR/TE, 600/13) shows 85 x 90 mm,
well-circumscribed mass in myometrium of corpus uteri as hyperintense with
hypointense amorphous bands.
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Fig. 2B —65-year-old woman with abdominal pressure (typical case).
Axial turbo spin-echo T2-weighted MR image (4,000/106) shows mass as
hyperintense with hypointense amorphous bands and chemical shift artifact
along frequency direction in mass (arrows).
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Fig. 2C —65-year-old woman with abdominal pressure (typical case).
Fat-suppression chemical shift selective axial spin-echo T1-weighted MR image
(500/13) shows signal suppression of hyperintense region on T1-weighted image
(A).
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Fig. 2D —65-year-old woman with abdominal pressure (typical case).
Fat-suppressed, gadolinium-enhanced axial spin-echo T1-weighted MR image
(500/13) shows strong enhancement of amorphous bands.
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Results
The MRI appearances of nine patients with uterine lipoleiomyoma are
summarized in Table 1. The
maximal diameter of the tumors ranged from 3.5 to 11 cm (mean, 7.5 cm). All
the lesions were well circumscribed. Tumor location was the myometrium of the
uterine corpus in six patients and the subserosa of the uterine corpus in
three. On T1-weighted images, the lesions exhibited hyperintensity with
hypointense amorphous bands in seven patients (Figs.
1A,
1B,
1C,
1D and
2A,
2B,
2C,
2D,
2E) and slight hypointensity
with hyperintense spots in two patients (Fig.
3A,
3B,
3C,
3D). All hyperintense areas on
T1-weighted images, which were suppressed on CHESS sequences, reflected fat
tissue pathologically. On T2-weighted images, the lesions exhibited
hyperintensity with hypointense amorphous bands in seven patients (Figs.
1A,
1B,
1C,
1D and
2A,
2B,
2C,
2D,
2E), a mixture of
heterogeneously hypo- and hyperintensity in one patient (Fig.
3A,
3B,
3C,
3D), and heterogeneous
hyperintensity in one patient. These hypointense and hyperintense areas on
T2-weighted image in patient 8 reflected pathologically stromal hyalinization
and stromal edematous change, respectively. This heterogeneously hyperintense
region on T2-weighted images in patient 9 reflected stromal myxomatous change.
T2-weighted images showed chemical shift artifact along the frequency
direction in the mass in four (45%) of nine patients (Figs.
1A,
1B,
1C,
1D,
2A,
2B,
2C,
2D,
2E,
3A,
3B,
3C,
3D). The hypointense areas on
T1- and T2-weighted images in four patients were strongly enhanced by contrast
material (Fig. 2A,
2B,
2C,
2D,
2E), reflecting smooth muscle
or fibrous tissue pathologically.
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Fig. 3A —64-year-old woman with abdominal pressure (atypical case). Axial
spin-echo T1-weighted MR image (TR/TE, 650/12) shows 9 x 10 cm,
well-circumscribed mass in myometrium of corpus uteri as slightly hypointense
with slightly hyperintense area and very hyperintense spots
(arrows).
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Fig. 3B —64-year-old woman with abdominal pressure (atypical case). Axial
turbo spin-echo T2-weighted MR image (3,500/96) shows mass as heterogeneously
mixed hypo- and hyperintensity and chemical shift artifact along frequency
direction in mass (arrow).
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Fig. 3C —64-year-old woman with abdominal pressure (atypical case).
Fat-suppressed chemical shift selective axial spin-echo T1-weighted MR image
(650/12) shows signal suppression of very hyperintense spots (arrows)
on T1-weighted image (A).
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Discussion
Lipomatous uterine tumors are uncommon. Approximately 180 cases have been
reported in the literature. According to previous reports, the incidence
ranged from 0.03% in hysterectomy specimens to 0.20% in uterine leiomyomas
[1,
2]. Pathologically, lipomatous
uterine tumors have been categorized into three groups
[3,
4]. The first group is pure
lipoma, which is composed of mature fat cells only and is encapsulated
[5]. The second group consists
of lipoleiomyoma
[6-9],
angiomyolipoma [10],
fibromyolipoma [11], and so
on; that is, mixed tumors containing various mesodermal tissue components such
as adipose fat, smooth muscle cells, a fibrous component, and connective
tissue. These neoplasms are also well-encapsulated benign growths. The third
and rarest group is malignant neoplasm, liposarcoma, which consists of
less-differentiated fat cells that have under-gone sarcomatous change
[12]. Lipoleiomyoma is the
most common entity in these three categories. Although the origin of
lipomatous lesions of the uterus has been the subject of much speculation,
three theories are common: direct metaplasia of smooth muscle or connective
tissue into fat cells, differentiation from misplaced embryonic fat cells, and
proliferation of accompanying perivascular fat cells into the blood vessels
[2,
3].
Uterine lipoleiomyoma occurs most frequently in postmenopausal women from
50 to 70 years old. This entity has been reported to range from 3 mm to 32 cm
in diameter (average, between 5 and 10 cm). It is usually well circumscribed
with a thin connectivetissue capsule. It is most frequently located in the
posterior wall of the uterine corpus; 10% or more are also seen in the uterine
cervix. This lesion is often associated with common leiomyomas
[1-4].
Several case reports have described the MRI finding of uterine
lipoleiomyoma, and all reports described typical cases containing abundant fat
tissue in the mass
[6-9].
This entity typically presents as a well-demarcated mass that is hyperintense
with hypointense amorphous bundles on T1- and T2-weighted images with chemical
shift artifact. The hyperintense region is suppressed on CHESS sequences. The
MRI characteristics observed in our series were variable and depended on the
volume of mesodermal tissue such as fat, muscle, connective tissue, and
stromal degeneration making up the lesion. Seven (78%) of nine cases with
abundant fat tissue in the mass presented typical MRI findings as described in
previous reports.
However, two cases (22%) with a small volume of fat tissue showed slight
hypointensity with a small hyperintense area on T1-weighted images and various
signal intensities on T2-weighted images because the stroma of the lesion
showed various degeneration. Even in these two atypical cases, CHESS imaging
was useful for the identification of a small fat component. Double-echo
gradient-echo chemical shift MRI (in-phase and opposed-phase imaging), which
was not used in our series, may also be useful to detect a small volume of fat
in the mass [13]. Because the
presence of a hyperintense area in the uterine mass on T1-weighted images is
usually associated with hemorrhage in uterine leiomyosarcoma, a
fat-suppression MRI sequence is important because of its ability to
differentiate fat tissue and hemorrhage.
Our study has some limitations because of its retrospective nature, small
sample size, and use of two types of MR equipment. The axial images were
obtained on the body axis, not on the uterine axis, in most patients. In this
context, further study should be conducted.
In conclusion, MRI including a fat-suppression sequence is a useful
technique to diagnose uterine lipoleiomyoma, with its high sensitivity and
specificity to fat and with its multisectional ability to show the precise
location of the lesion. Although it is not always possible to differentiate
uterine lipoleiomyoma from other uterine lipomatous tumors (angiomyolipoma,
fibromyolipoma, myelolipoma, liposarcoma, and so on) on MRI, it is important
to become familiar with the wide variety of MRI findings of this entity
because a correct preoperative diagnosis is critical to determine appropriate
treatment and to avoid unnecessary intervention.
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Abstract
Introduction
