AJR 2003; 181:1079-1081
© American Roentgen Ray Society
Radiography, Doppler Sonography, and MR Angiography of Malignant Pulmonary Hemangiopericytoma
Erkan Yilmaz1,
Atila Akkoclu2,
Aydanur Kargi3,
Can Sevinc2,
Nuray Komus2,
Hudai Catalyurek4 and
Unal Acikel4
1 Department of Radiology, Dokuz Eylül University School of Medicine,
35340, Izmir, Turkey.
2 Department of Chest Diseases, Dokuz Eylül University School of Medicine,
35340 Izmir, Turkey.
3 Department of Pathology, Dokuz Eylül University School of Medicine,
35340, Izmir, Turkey.
4 Department of Thoracic Surgery, Dokuz Eylül University School of
Medicine, 35340, Izmir, Turkey.
Received September 4, 2002;
accepted after revision February 3, 2003.
Address correspondence to E. Yilmaz, Mithatpasa Cad. Tan Apt. 65/3,
TR-35330 Balcova, Izmir, Turkey.
Introduction
Hemangiopericytoma is a rare mesenchymal tumor believed to originate from
the capillary pericytes [1]. It
may affect every organ but most commonly occurs in the musculoskeletal system,
skin, and retroperitoneum. Primary hemangiopericytoma of the lung is extremely
rare [1,
2]. We report the imaging
findings of a histologically proven case of primary pulmonary
hemangiopericytoma in a male patient using radiography, CT, and MRI. We also
describe Doppler sonography and MR angiography findings that, to the best of
our knowledge, have not previously been reported.
Case Report
A 69-year-old man was admitted to our hospital with a 2-week history of
tenderness and swelling in both legs. The medical history of the patient was
unremarkable, but he had a history of smoking. Physical examination revealed
decreased breath sounds in his lower right chest and deformity of his fingers
consistent with clubbing. Laboratory results were normal except for a mildly
elevated sedimentation rate of 31 mm/hr.
Chest radiography showed a large, homogeneous masslike opacity in the right
lower zone (Fig. 1A).
Unenhanced CT confirmed the presence of a large tumor (23 x 21 x
16 cm) involving nearly half of the right lower hemithorax. The tumor,
containing foci of hyperdense areas, was well circumscribed and compressed,
surrounding lung parenchyma cranially (Fig.
1B). CT enhancement of the hyperdense areas was 50–80 H,
which is suggestive of hemorrhage. After injection of an iodinated contrast
agent, the tumor showed nonhomogeneous contrast enhancement with central,
low-attenuation regions consistent with necrosis. No evidence of metastasis to
other regions of the lung or regional lymph adenopathy was found. Gray-scale
sonography revealed a well-defined, hypoechoic solid mass at the lower region
of the right lung. Consecutive evaluation with color and pulsed Doppler
sonography showed a highly vascular tumor containing several venous flows,
some of which had a pulsatile waveform, probably in the returning veins as a
result of arteriovenous shunting and few arterial flows. Spectral waveforms of
two arterial flows at the periphery of the tumor were suggestive of
arteriovenous shunting, with the peak Doppler frequency shift exceeding 3.5
kHz (Fig. 1C).
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Fig. 1B. —69-year-old man with pulmonary hemangiopericytoma. Unenhanced
CT scan at lung base reveals well-marginated mass with high-attenuation area
(50–80 H) due to intratumoral hemorrhage (arrows). Mediastinal
and peripleural fat planes are also intact.
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Fig. 1C. —69-year-old man with pulmonary hemangiopericytoma. Color
Doppler sonogram shows well-defined hypoechoic mass overlying diaphragm
(arrow). Note central and peripheral color flows in tumor. Spectral
arterial waveform shows low-impedance arterial flow with high systolic and
diastolic velocities (upper portion). Pulsatility index is 0.90,
resistive index is 0.51, and peak frequency shift is 3.9 kHz. Venous waveform
shows pulsatile flow with high velocities (lower portion).
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MRI was performed to evaluate the mediastinal structures and chest wall
around the tumor as well as its vascular structure in more detail. The tumor
was well encapsulated and isointense relative to the skeletal muscles on
T1-weighted images and heterogeneously hyperintense on T2-weighted images. The
tumor had hyperintense areas on both T1- and T2-weighted images that were
compatible with hemorrhage. T1-weighted imaging performed after administration
of gadolinium-dimeglumine showed scattered areas of strong enhancement,
especially at the periphery of the lesion
(Fig. 1D). Furthermore, a few
linear structures of high signal suggestive of small vessels were detected in
the tumor. On the basis of the imaging results, a highly vascular mesenchymal
neoplasia arising from lung tissue was diagnosed. Catheter angiography was
planned, but the patient refused. Therefore, because of vessels shown on
Doppler sonography and MRI, MR angiography was performed using a
three-dimensional fast gradient-echo sequence in the coronal plane after
administration of contrast material. MR angiography showed short and linear
signals reflecting small blood vessels in the tumor. Parenchymal vascularity
around the tumor was found to be slightly higher than in the other regions of
the right lung tissue, suggesting that multiple arteries were feeding the
tumor from the tributaries of the right pulmonary artery
(Fig. 1E).
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Fig. 1D. —69-year-old man with pulmonary hemangiopericytoma.
Fat-saturated gadolinium dimeglumine–enhanced T1-weighted fast spin-echo
image shows tumor to be inhomogeneous with intensely enhancing nodules
(arrows) peripherally.
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Fig. 1E. —69-year-old man with pulmonary hemangiopericytoma. Coronal
contrast-enhanced MR angiogram shows highly vascular tumor containing numerous
signal intensities corresponding to pulmonary vessels encased by tumor. Tumor
is supplied by several distorted branches of right pulmonary artery (white
arrow). Note relatively large vessels (black arrows) surrounding
tumor, which are suggestive of circumferential drainage veins.
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Transthoracic fine-needle aspiration of the tumor was insufficient for
diagnosis. Therefore, a thoracotomy was performed. An inferior bi-lobectomy
was performed with complete excision of the tumor. On gross examination, a
large, roughly spherical mass involving most of the right lower lobe and part
of the middle lobe was found. The mass measured 18 cm in the greatest
dimension and was well demarcated from the surrounding lung parenchyma. The
cut surface was predominantly solid and pale gray, with multiple areas of
necrosis and hemorrhage. At microscopic examination, the neoplasm was seen to
comprise densely packed spindle-shaped and ovoid cells that were separated by
numerous thin-walled, dilated, and anastomosing vascular channels showing
focal areas of typical staghorn configuration
(Fig. 1F). The appearances were
characteristic of malignant hemangiopericytoma. After surgery, the patient
received radiotherapy. On follow-up at 3 months, the patient was well and had
no signs of recurrence.
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Fig. 1F. —69-year-old man with pulmonary hemangiopericytoma.
Photomicrograph of pathology specimen shows richly vascular pattern consisting
of vessels of varying sizes, some of which form characteristic staghorn
configuration (arrow). (H and E, x40)
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Discussion
Hemangiopericytoma is a rare mesenchymal tumor occurring at any age but
most commonly in the fifth and sixth decades
[1,
2]. It accounts for less than
2% of all soft-tissue sarcomas
[1]. The definitive origin of
this neoplasia is not clear, but most authorities believe that it arises from
pericytes around small blood vessels
[3]. Primary pulmonary
involvement is extremely uncommon.
Macroscopically, hemangiopericytoma generally appears as a well-demarcated
mass, sometimes with areas of hemorrhage and necrosis. The growth of the tumor
is slow and expansive, with a gradual compression of surrounding tissues that
results in the formation of a fibrous pseudocapsule. The tumor therefore does
not invade the surrounding tissue and usually presents very late
[4], as it did in our patient.
Histologically, hemangiopericytomas are composed of tightly packed tumor cells
situated around thin-walled endothelium-lined vascular channels that resemble
moose antlers or staghorns. The vascular channels, which range from
capillary-sized vessels to large gaping sinusoidal spaces, may be dilated and
tortuous and can anastomose with one another
[3,
5].
The radiology literature has reported a total of five cases of primary
pulmonary hemangiopericytoma from two studies. In both, emphasis is placed on
radiographic, CT, and MRI features
[6,
7]. However, to our knowledge,
MR angiography and Doppler sonography findings of hemangiopericytoma arising
in the lung have not been documented. On chest radiography, it is often seen
as a well-outlined mass. Unenhanced CT may reveal tumoral calcifications;
after contrast material injection, CT may show an inhomogeneous mass with
areas of low attenuation due to necrosis
[6,
7]. MRI often reveals
hemorrhage, which is a common histologic finding. CT and MRI also show the
relationship between the tumor and adjacent structures such as the chest wall
and mediastinum.
Hemangiopericytoma is a highly vascular tumor that usually contains dilated
vessels and occasionally may cause significant arteriovenous shunting
[5]. Hemangiopericytoma is
rarely seen in the lung despite the rich vascularity of pulmonary tissue
[6]. Angiography is helpful in
showing the feeding artery of this richly vascular tumor and typically stains
densely in the arterial phase and occasionally shows the early-draining veins
[2]. Intratumoral arteriovenous
shunting may be suspected on Doppler sonography on the basis of the presence
of low-impedance flow with high peak systolic and end diastolic velocities in
the feeding arteries and the arterialization of the venous flow with increased
pulsatility [8].
Hemangiopericytoma must be distinguished from the more common sarcomas,
such as malignant fibrous histiocytoma and angiosarcoma, which contain areas
of rich hemangiopericytoma like vascularity
[2].
The biologic behavior of hemangiopericytoma can vary from benign to
malignant depending on the tumor size, mitotic rate, degree of cellularity,
presence of immature or pleomorphic tumor cells, and foci of hemorrhage and
necrosis [4,
6]. The main treatment of
choice is wide surgical excision. Although there is no consensus, adjuvant
high-dose radiotherapy and chemotherapy have been suggested because the
malignant variety has a high risk of local recurrence and distant metastases
[4].
Acknowledgments
We thank Rachel Ann Cooper for manuscript preparation.
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Introduction
Case Report
