AJR 2001; 177:244-245
© American Roentgen Ray Society
Late Pulmonary Metastases from Hemangiopericytoma of the Mandible
Unusual Findings on CT and MR Imaging
James G. Ravenel1 and
Philip C. Goodman
1
Both authors: Department of Radiology, Box 3808, Duke University Medical
Center, Durham, NC 27710.
Received September 27, 2000;
accepted after revision November 16, 2000.
Address correspondence to J. G. Ravenel.
Introduction
Hemangiopericytomas are unusual vascular tumors that originate from the
pericytes located just outside the capillary walls. Hemangiopericytomas have
features that may pathologically resemble soft-tissue sarcomas, hemangiomas,
and glomus tumors. Hemangiopericytomas were first described as a unique entity
by Stout and Murray in 1942
[1]. Behavior is variable, and
these tumors can metastasize early or late. We recently encountered a
hemangiopericytoma metastatic to the lungs 20 years after its initial
resection from the mandible. This particular tumor contained large vascular
spaces, a feature described pathologically but, to our knowledge, not
previously seen on CT or MR imaging. We review the characteristics and imaging
features of this rare tumor.
Case Report
A 58-year-old woman presented with a chronic cough that had been worsening
for more than 1 year. She had originally been diagnosed with a
hemangiopericytoma of the mandible 20 years earlier. At that time, she was
treated initially with local resection, but recurrent disease required five
additional operations, culminating in a mandibulectomy and reconstruction 17
years before her current physician visit. Until the cough developed, she had
no interval medical problems.
When symptoms did not improve, chest radiography and subsequent
contrast-enhanced CT revealed multiple pulmonary nodules and masses
(Fig. 1A). The largest mass, in
the right lower lobe, measured 10 cm and had large enhancing vessels centrally
revealed on CT (Fig. 1B). At MR
imaging, the mass was similar in signal intensity to muscle on T1-weighted
images and showed increased signal intensity on T2-weighted images
(Fig. 1C). After gadolinium
administration, relatively homogeneous enhancement and central flow voids were
seen that corresponded to the large vessels identified on CT
(Fig. 1D).
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Fig. 1A. —58-year-old woman with metastatic hemangiopericytoma.
Representative axial CT scan at level of left atrium shows multiple bilateral,
well-defined, solid pulmonary nodules as large as 3 cm. Abnormal left rib is
result of prior resection for bone graft.
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Fig. 1C. —58-year-old woman with metastatic hemangiopericytoma.
Fat-suppressed axial fast spin-echo T2-weighted MR image (4285/98, TR/TE) at
approximately same level as B reveals large mass to have homogeneously
increased signal. Prominent signal voids corresponds to enlarged vessels seen
on B. Note right pleural effusion and bilateral pulmonary
metastases.
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Fig. 1D. —58-year-old woman with metastatic hemangiopericytoma.
Gadolinium-enhanced coronal spin-echo T1-weighted MR image (606/9) shows
homogeneous enhancement of right lower lobe mass with multiple signal flow
voids representing large tumor vessels. Note separate metastasis in left upper
lobe.
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Discussion
Hemangiopericytomas are rare tumors that can involve any region of the
body, although the most common locations are the lower extremity, the
retroperitoneum, and, in up to 16% of cases, the head and neck
[2]. Hemangiopericytomas have
been described in all age groups, with more than 40% occurring in the fifth
and sixth decades. Hemangiopericytomas have been classified as histologically
benign or malignant, although this distinction is controversial. When only the
"malignant" type are studied, metastases are seen frequently
(>75% of the time) [3].
Overall, local and distant recurrences are seen in as many as 50% of cases
[4], with distant metastases
seen in more than 15% of all cases
[3,
4]. Metastases to lung or bone
frequently follow one or more local recurrences. In our patient, multiple
local recurrences required treatment before the eventual appearance years
later of distant metastatic disease.
Conventional radiographs are rarely diagnostic of hemangiopericytoma in any
region of the body. The most common finding for a primary lesion is a
nonspecific soft-tissue mass; approximately 10% contain speckled calcification
[3]. Pulmonary metastases are
seen as one or more well-defined nodules or masses, but the appearance is
nonspecific. The reports of chest radiographs of metastatic disease do not
discuss the prevalence of calcifications, but calcification on CT has
occasionally been noted in primary pulmonary hemangiopericytomas
[5]. No reports document the
frequency of calcification in lung metastases.
CT and MR imaging are the usual techniques for evaluating
hemangiopericytomas. Characteristically, large soft-tissue masses, often with
homogenous enhancement or large cystic spaces interspersed among areas of
solid enhancement, are described on CT
[6,
7]. The enhancement pattern
suggests the highly vascular nature of these tumors. Speckled calcifications
may also be detected. Larger masses may undergo central necrosis.
MR imaging findings are well described for central nervous system
hemangiopericytomas. Most tumors are isointense to gray matter on both T1- and
T2-weighted images and display heterogeneous enhancement after gadolinium
administration [8]. MR studies
outside the central nervous system have been described in case reports and
consist of intermediate T1 and hyperintense T2 signal intensity
[9]. To our knowledge, no large
series has been performed to document the spectrum of MR findings. Two
pulmonary hemangiopericytomas imaged by MR imaging showed heterogeneous hypo-
and hyperintense T1 and hyperintense T2 signal intensity with both cystic and
hemorrhagic regions [5].
Contrast material was not administered in these two patients.
In the past, angiography was often used in the workup of these cases.
Reports have documented that angiography of hemangiopericytomas reveals their
highly vascular nature, with an increase in both the size and number of
feeding arteries and draining veins. The tumors may have either a homogeneous
or mottled appearance [6].
The CT and MR imaging characteristics in our patient show a mix of the
previously described CT, MR imaging, and angiographic findings. Homogeneous
enhancement was seen with both iodinated contrast material and gadolinium, but
necrosis and hemorrhage were not evident, even in the largest metastases. On
both contrast-enhanced CT and MR imaging, large vessels up to 2 cm in diameter
were present within the tumor. These large vessels were manifest as enhanced
vessels on CT scans with the same intensity as hepatic vasculature and as flow
voids on both T1- and T2- weighted MR images.
Although they are rare, hemangiopericytomas metastasize in 15-37.5% of
patients in large series [2,
3], with the first metastasis
recorded 5 years after the primary diagnosis in 5-10% of cases
[3,
5]. Our patient adds to this
experience, with metastatic disease appearing 17 years after the last local
recurrence. Careful surveillance is necessary for early detection because
metastasectomy is an accepted treatment option for a solitary metastasis. CT
and MR imaging may be useful in delineating the extent of disease and may
suggest the diagnosis if characteristic findings are seen.
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Introduction
Case Report
