AJR 2001; 176:463-464
© American Roentgen Ray Society
Intravascular Femoral Vein Lipoma
An Unusual Cause of Lower Limb Venous Obstruction
Mark J. McClure1,
Josée Sarrazin1,
Linda Kapusta2,
John Murphy1,
Anna-Marie Arenson1 and
William Geerts3
1
Department of Radiology, Sunnybrook and Women's College Health Sciences
Centre, MG-164, 2075 Bayview Ave., Toronto, Ontario M4N 3M5, Canada.
2
Department of Pathology, Sunnybrook and Women's College Health Sciences
Centre, Toronto, Ontario M4N 3M5, Canada.
3
Department of Medicine; Sunnybrook and Women's College Health Sciences Centre,
Toronto, Ontario M4N 3M5, Canada.
Received April 3, 2000;
accepted after revision July 12, 2000.
Address correspondence to J. Sarrazin.
Introduction
Lipomas arising within veins have most commonly been described in
association with the inferior vena cava. They are considered an incidental
finding with a frequency of 0.35% in abdominal CT examinations
[1]. Intravascular lipomas
involving the superior vena cava are rare
[2,
3]; one case previously
documented a lipoma extending into a brachiocephalic vein
[3]. A recent report describes
a lipoma arising from the soft tissues of the thigh, causing extrinsic
compression on the femoral vein, with resultant chronic deep venous thrombosis
[4]. To our knowledge, there
are no previous reports of an intraluminal lipoma arising within the wall of
the femoral vein causing symptomatic venous obstruction.
Case Report
A 76-year-old previously healthy man noted painless swelling of the left
calf after a 2-hr air-plane flight. The swelling persisted for 18 months and
eventually progressed to involve the thigh. He had no risk factors for deep
venous thrombosis. On physical examination, the patient appeared healthy apart
from nontender swelling of the entire left lower limb and distended
superficial veins in the calf. Results of hematologic and biochemical profiles
were normal. Doppler sonography of the left leg revealed a noncompressible
echogenic intraluminal mass, approximately 2 cm in length
(Fig. 1A), causing local
expansion of the common femoral vein. Minimal flow was seen anterior to the
lesion with aliasing surrounding the severely stenotic segment. A diagnosis of
localized common femoral vein thrombosis was made, and oral anticoagulation
therapy was started.
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Fig. 1A. —76-year-old man who presented with progressive left leg
swelling and discomfort. Sagittal sonogram of left common femoral vein shows
intraluminal echogenic material (calipers) within venous lumen.
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Because of the discrepancy between the severe and prolonged leg swelling
and the localized thrombus suggested on sonography, CT was performed to
exclude a pelvic mass (Figs. 1B
and 1C). The IV
contrast—enhanced CT examination showed a 2-cm intraluminal lesion of
fat attenuation (-112 H) distending the lumen of the common femoral vein. The
mass extended posterolaterally through the vein wall into the intermuscular
soft tissues of the thigh. The patient was referred to a vascular surgeon for
resection of the lesion because of its associated symptoms and the need for
ongoing anticoagulation to prevent venous thrombosis.
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Fig. 1B. —76-year-old man who presented with progressive left leg
swelling and discomfort. Contrast-enhanced CT scan shows fatty mass (-112 H)
within left common femoral vein (asterisk). Increased fat surrounding
left common femoral vessels corresponds to extraluminal component of mass.
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A venogram (Fig. 1D) and MR
image of the left leg were obtained for surgical planning. The mass was of
high signal intensity on T1-weighted images
(Fig. 1E) and intermediate
signal intensity on T2-weighted images; the mass showed uniform signal drop on
fat-suppressed sequences. There was no evidence of a hemorrhagic component or
invasion of adjacent structures.
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Fig. 1D. —76-year-old man who presented with progressive left leg
swelling and discomfort. Venogram of left leg shows intraluminal extent of
filling defect (asterisk). Extraluminal component can also be seen as
subtle relative lucency (arrows) on this oblique projection.
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Fig. 1E. —76-year-old man who presented with progressive left leg
swelling and discomfort. Sagittal T1-weighted MR image reveals intraluminal
component of lesion extending posteriorly through vein wall (V), between
muscle planes (arrows).
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At surgery, the intravascular lesion and its posterior extension were
resected, and a venous graft was interposed at the resection site. Pathology
revealed a benign lipoma arising from the venous wall
(Fig. 1F). Within days after
surgery, the leg swelling decreased dramatically. Anticoagulants were
discontinued 3 months after surgery.
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Fig. 1F. —76-year-old man who presented with progressive left leg
swelling and discomfort. Photomicrograph of resected surgical specimen shows
vein endothelium and adventitia. Note attenuation of wall in region of defect
(arrow).
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Discussion
Intravascular lipomas are uncommon lesions and, to our knowledge, have not
previously been described in the femoral vein or as a cause of leg swelling.
Other primary tumors originating from vein walls are also rare; these include
leiomyomas and leiomyosarcomas
[5], hemangiomas
[6], and angiosarcomas
[7]. Intravascular lipomas have
been reported to occur in the inferior vena cava in approximately 0.35% of CT
examinations [1] and are even
less common in the superior vena cava.
Doppler sonography is a reliable tool for detecting deep venous thrombosis.
However, the potential of sonography to distinguish between an intravascular
soft-tissue lesion and a localized thrombus is limited. In our patient we
identified an echogenic intraluminal mass that caused distention of the vein.
The noncompressible nature of the lesion and near-absent flow were consistent
with an intravascular thrombus. However, the clinical history and physical
examination were inconsistent with the radiologic findings, prompting further
investigation.
The IV contrast—enhanced CT examination of the pelvis revealed a mass
of fat attenuation within the common femoral vein extending posteriorly
through the venous wall. Sonography failed to reveal this extravascular
component because of the iso-echogenicity of the mass relative to the normal
perivascular fat.
The venogram was helpful in showing the intraluminal extent of the lesion
before surgery MR examination aided surgical planning by characterizing the
soft-tissue content of the lesion, delineating the extent of the extravascular
component, and revealing the lack of invasion into adjacent structures.
There have been reports of lipomas arising from the wall of the superior
and inferior vena cava. However, the pathology literature does not clearly
describe whether a lipoma associated with blood vessels arises from the wall
itself or external to it [1].
The media layer of veins is poorly developed, predisposing these vessels to
compression and easy penetration by malignant tumors
[8]. We postulate that the
lipoma arose from within the vessel wall, because the transgression of a
benign lipoma through the wall of a vein appears to be highly unusual.
This is the first known report of a femoral vein lipoma. As this case
illustrates, Doppler sonography may fail to discriminate between a localized
thrombus and other intravascular soft-tissue lesions. In cases in which there
is a discrepancy between the clinical features and the size or extent of a
thrombus on sonography, other imaging modalities should be considered. In our
patient, the additional tests were useful in determining the tissue
characteristics of the lesion and permitted a definitive diagnosis before
surgery.
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