AJR 2002; 179:637-639
© American Roentgen Ray Society
Giant Bilateral Inflammatory Pseudotumor Arising Along the Arterial Sheath of the Lower Extremities
Marius Horger1,
Markus Müller-Schimpfle1,
Manfred Wehrmann2,
Brigitte Mehnert3,
Franz Maurer4,
Susanne M. Eschmann5 and
Claus C. Claussen1
1 Department of Diagnostic Radiology, Eberhard-Karls-Universität,
Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany.
2 Department of Pathology, Eberhard-Karls-Universität, Liebermeisterstr. 8,
72076 Tübingen, Germany.
3 Department of Internal Medicine, Eberhard-Karls-Universität,
Ottfried-Müller-Str. 5, 72076 Tübingen, Germany.
4 Department of Traumatologic and Orthopedic Surgery,
Eberhard-Karls-Universität, Schnarrenbergstr. 95, 72076 Tübingen,
Germany.
5 Department of Nuclear Medicine, Eberhard-Karls-Universität,
Röntgenweg 13, 72076 Tübingen, Germany.
Received December 17, 2001;
accepted after revision February 13, 2002.
Address correspondence to M. Horger.
Introduction
Inflammatory pseudotumor, also known as inflammatory myofibroblastic or
histiocytic tumor, is a cellular infiltrate of lymphocytes, plasma cells,
histiocytes, and other immune-reactive cells surrounded and infiltrated by
varying degrees of proliferative stroma. The similarity to malignancies is
striking in most cases. Inflammatory pseudotumors are usually
well-circumscribed, multinodular masses that have been described in most organ
types and in juxtaneural and juxtavascular locations
[1]. However, to our knowledge,
no articles have described a bilateral manifestation in the location and at
the extent that we present.
Case Report
A 44-year-old man observed a progressive, initially nonpainful swelling of
both popliteal fossae over a period of 3 years 6 months. A few months after
onset, the neighboring calf and thigh regions showed identical symptoms, and
the patient had pain that increased with knee flexion. A posteriorly located
mass of coarse resistance in the lower thigh and upper calf was noted at
palpation. Laboratory analysis, including autoantibody and tumor marker
determination, revealed no abnormalities.
MR imaging of the knees and thighs was performed on a 1.5-T unit (Vision;
Siemens Medical Systems, Erlangen, Germany). On T1-weighted images (TR/TE,
570/14), the mass showed isointense signal relative to muscle
(Fig. 1A). On turbo inversion
recovery images (6846/60), low signal dominated
(Fig. 1B). After IV
administration of gadopentetate dimeglumine (Magnevist; Schering, Berlin,
Germany), the entire mass enhanced intensely but slightly heterogeneously
(Fig. 1C). The initial extent
of the mass was 40 x 4.0 x 4.5 cm on the right side and 26 x
4.0 x 3.5 cm on the left side. The popliteal artery was encased but
still patent at full length. The popliteal vein showed signs of partial
compression and was massively displaced by the tumor. A soft-tissue edema
reaching the gluteal and groin region was visualized at the periphery of this
mass.
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Fig. 1B. —44-year-old man with bilateral inflammatory pseudotumor of
lower extremities. Turbo inversion recovery sagittal MR image shows low-signal
mass (arrow) with moderate surrounding edema.
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Fig. 1C. —44-year-old man with bilateral inflammatory pseudotumor of
lower extremities. Contrast-enhanced T1-weighted MR image reveals strong
enhancement of mass and vascular encasement (arrow, right and left
sides).
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FDG positron emission tomography was performed on an Advance PET scanner
(General Electric Medical Systems, Milwaukee, WI). A whole-body scan revealed
hypermetabolism at the site of the pseudotumor with a standard uptake value of
5.8 for FDG. Further areas of hypermetabolism were found along the thighs up
to the groin (Fig. 1D).
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Fig. 1D. —44-year-old man with bilateral inflammatory pseudotumor of
lower extremities. FDG positron emission tomography image shows hypermetabolic
conglomerates in left popliteal region (long arrows) with extension
up thighs (short arrows).
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An attempt at surgical resection 2 years later failed because of
intraoperative injury of the popliteal artery as a result of the infiltrative
character of the pseudotumor growth. Also the proximity of the tumor to the
neurovascular bundle of the lower limbs compromised the possibility of
complete resection.
The next therapy option was a high-dose systemic steroid via oral
administration beginning with 160 mg prednisolone (Decortin H; Merck,
Darmstadt, Germany). The dose was progressively reduced over 6 months, during
which the mass size decreased by 40-50%
(Fig. 1E). The accompanying
soft-tissue edema also diminished. After another 6 months, with the patient
still recieving low-dose steroid therapy (7 mg of Decortin H), the tumor
showed further but only minimal regression and the gadopentetate dimeglumine
enhancement also decreased.
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Fig. 1E. —44-year-old man with bilateral inflammatory pseudotumor of
lower extremities. Contrast-enhanced T1-weighted axial MR image documents
shrinkage of mass (arrow, right and left sides) under steroid
therapy.
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At follow-up 1 year later, after interruption of the steroid therapy
because of Cushing's syndrome appearances, the mass revealed a moderate
increase in size, and the accompanying edema was also progressive. Treatment
with nonsteroidal antiinflammatory drugs was not effective.
Two biopsies, the first performed at the time of the first diagnosis (3
years 6 months after onset of symptoms) and the other 2 years later at the
surgical debulking attempt, showed a follicular lymphatic hyperplasia and an
accumulation of other immunoreactive cells as plasma cells, mast cells, and
histiocytes surrounded by a fibrous stroma. The polyclonal and polymorphic
nature of the inflammatory cells was confirmed by molecular biologic and
immunohistochemical studies. Further histopathologic reevaluations of the
tissue samples carried out by the federal reference center confirmed the
diagnosis of an inflammatory pseudotumor, excluding lymphoma or low-grade
sarcoma (Fig. 1F).
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Fig. 1F. —44-year-old man with bilateral inflammatory pseudotumor of
lower extremities. Photomicrograph of histopathologic specimen shows
aggregates of lymphocytes, plasma cells, mast cells, and abundant histiocytes
in myxoid and fibrous stroma. (H and E, x200)
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Discussion
The inflammatory pseudotumor is a disease process described as a
circumscribed mass of inflammatory cells usually involving a single organ
system. At presentation, it is frequently misinterpreted as a malignancy. In
our patient, the mass originated along the wall of the popliteal and femoral
arteries in a striking bilateral fashion, reached unusual extension, and
showed local invasive spread.
Usually the inflammatory pseudotumor is treated by surgical excision with
good long-term results. In cases of inoperability or only partial
resectability, as here, patients are given steroid therapy that results in
long-term remission. In the case we present, the pathologic process was
temporarily halted under corticosteroid therapy; at 5 years after the initial
manifestation the patient had no further disease manifestations in other
locations [2]. However, the
patient refused permanent steroid therapy because of secondary Cushing's
syndrome appearances; the pseudotumor then continued its progress.
Particularly interesting in this case was the bilateral nature of the
disease process. According to the patient's history, the mass appeared in both
extremities at the same time but to an asymmetric extension; we believe that
this distribution pattern reflects true synchronicity of the disease.
To our knowledge, no reports describe a relationship between inflammatory
pseudotumor and a long-standing ankylosing spondylitis or a high familial
frequency of collagenous diseases, but both were present in this patient's
history and may be significant in the etiology of the case. Similar cases have
been described in which malignancy simulated inflammatory pseudotumor
accompanying Wegener's granulomatosis
[3] or Behçet's syndrome
[4]. Another similar case of
benign myofibroblastic pseudosarcomatous proliferation was published by Sheikh
et al. [5] and described as
intravascular fasciitis with the nodular fasciitis as prototype. MR imaging
could not differentiate this entity from other soft-tissue tumors that are
rich in fibrous stroma, such as aggressive fibromatosis, myxoinflammatory
fibroblastic sarcoma [6],
fibroelastoma, or other entities such as neurofibromatosis, lymphoma, or
sarcoidosis.
In our patient, MR imaging was well suited for documentation of the
preoperative extent and surveillance. The enhanced studies showed correlation
between gadopentetate dimeglumine uptake and activity of this process at
follow-up. FDG positron emission tomography performed as a whole-body survey
helps to improve the definition of involved body areas
[7,8,9].
However, for treatment planning and monitoring of therapy effects, MR imaging
is the method of choice because of its superior depiction of the exact tumor
location and of the tumor-related effects (edema) and the perfusion changes
under medical treatment.
The presented case of an inflammatory pseudotumor is unique because of its
unusual extent and bilateral nature. MR imaging was helpful in showing the
characteristics of a hypervascular fibrotic mass with encasement of the blood
vessels. The good response to steroid therapy was documented with mass
morphology and perfusion.
Inflammatory pseudotumor is a rare, albeit possible, differential diagnosis
in similar cases, and the clinician should be aware of the potential
complications of primary surgical treatment.
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Introduction
Case Report
