AJR 2000; 175:475-476
© American Roentgen Ray Society
CT and MR Imaging of Orbital Metastasis from Islet Cell Carcinoma of the Pancreas
T. F. Gotwald1,2,
S. J. Zinreich1,
M. Schocke3,
T. Frede2,
R. Bellmann4 and
D. Zur Nedden2
1
Department of Radiology, Neuroradiology Division, Johns Hopkins Medical
Institutions, 600 N. Wolfe St., Baltimore, MD 21287.
2
Department of Radiology II, Neuroradiology Division, University Hospitals
Innsbruck, Anichstr. 35,6020 Innsbruck, Austria.
3
Department of Magnetic Resonance and Spectroscopy, University Hospitals
Innsbruck, 6020 Innsbruck, Austria.
4
Department of Internal Medicine, University Hospitals Innsbruck, 6020
Innsbruck, Austria.
Received October 18, 1999;
accepted after revision December 8, 1999.
Address correspondence to T. Gotwald.
Introduction
We report a rare case of orbital metastasis from an islet cell tumor of the
pancreas with a unique appearance on MR imaging. To our knowledge, this case
is the first to be reported with CT and MR imaging documentation.
Case Report
A 53-year-old woman was referred to the radiology department for restaging
of an islet cell carcinoma in the head of the pancreas after chemotherapy.
Liver and bone metastases were present before therapy. The patient's most
recent complaint was severe headache. Physical examination revealed a swollen
right orbital ridge with right-sided proptosis, diplopia, and partial visual
loss in the right eye.
Helical CT (Somatom Plus S40 spiral scanner; Siemens Medical Systems,
Erlangen, Germany) of the orbits was performed with and without IV
administration of 100 mL of iopromidol (Ultravist; Schering, Vienna, Austria).
MR imaging (1.5-T Magnetom Vision scanner; Siemens) of the orbits included
axial spin-echo T1-weighted sequences before and after IV administration of
gadopentetate dimeglumine. An axial fast spin-echo T2-weighted sequence and a
coronal spin-echo fat-suppressed T1-weighted sequence were performed after the
administration of IV contrast material.
CT revealed a mass in the superolateral quadrant of the right orbit.
Centrally, the mass had a low attenuation with peripheral enhancement after
the administration of IV contrast material
(Fig. 1A). Erosion of the
superolateral orbital wall was prominent, with infiltration into the temporal
muscle. In addition, erosion extended into the ventral wall of the middle
cranial fossa, with meningeal enhancement. The right globe was proptotic. The
T1- and T2-weighted MR images revealed a heterogeneous lesion of decreased
signal intensity in the superolateral quadrant of the orbit (Figs.
1B and
1C). After IV administration of
gadopentetate dimeglumine, circumferential enhancement of this lesion was
seen, with dural enhancement along the right ventral middle cranial fossa
(Fig. 1D). The meningeal
enhancement and the temporal muscle involvement were more prominent on the MR
imaging examination. There was also evidence of sinusitis involving the right
maxillary and ethmoidal sinuses.
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Fig. 1A. —53-year-old woman with malignant islet cell carcinoma of pancreas
and lesion to right orbit. Contrast-enhanced axial CT scan at level of orbits
reveals hypodense right lateral orbital mass (asterisk). Note
prominent erosion of lateral orbital wall (small arrow). Also note
dural enhancement along ventral middle cranial fossa (large
arrow).
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Fig. 1B. —53-year-old woman with malignant islet cell carcinoma of pancreas
and lesion to right orbit. Axial T1-weighted MR image through mid orbital
region shows low-signal-intensity lesion in right lateral orbit
(asterisk).
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Fig. 1C. —53-year-old woman with malignant islet cell carcinoma of pancreas
and lesion to right orbit. Axial T2-weighted MR image through mid orbital
region reveals hypointense signal mass (asterisk) and tumor invasion
into temporal muscle (arrow).
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Fig. 1D. —53-year-old woman with malignant islet cell carcinoma of pancreas
and lesion to right orbit. Contrast-enhanced coronal T1-weighted MR image
through orbits shows peripheral enhancement (small arrows)
surrounding lesion and dural enhancement (large arrow).
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After antibiotic therapy for sinusitis, the orbital tumor, including the
infiltrated temporal muscle, was surgically resected. The postoperative
histopathologic evaluation confirmed the diagnosis of metastatic islet cell
tumor. During surgery, the dura did not appear to be infiltrated. Follow-up MR
examinations 3 and 6 months later did not reveal tumor growth at this
site.
Discussion
Islet cell tumors of the pancreas are neoplastic proliferations arising
from endocrine cells (islets of Langerhans)
[1]. They may be associated
with multiple endocrine neoplasia and are hormone-producing in approximately
60% of cases. The biologic behavior is variable and often unpredictable. The
therapy of choice for these tumors is surgical excision; therefore, early
detection before extensive spread is crucial for complete resection. Islet
cell tumors of the pancreas metastasize to the liver, regional lymph nodes,
lungs, and bone [2,
3]. Metastasis from islet cell
carcinoma to other organs is rare. The most commonly known neoplasms that
metastasize to the orbit originate from lymphoma, breast carcinoma, lung
carcinoma, prostatic carcinoma, and melanoma
[4,
5].
The differential diagnosis of a superolateral quadrant orbital mass focuses
mostly on abnormalities affecting the lacrimal gland, such as leukemic
infiltration, inflammatory disease, or a tumor
[6]. The differential diagnosis
also includes dermoid cyst, lymphoma, glioma, hemangioma (capillary or
cavernous), hemangiopericytoma, meningioma, Wegener's granulomatosis,
sarcoidosis, other inflammatory pseudotumors, rhabdomyosarcoma, cholesterol
granuloma, intraorbital abscess, and metastases
[7].
In our patient, the radiographic evaluation showed the lacrimal gland to be
normal; therefore, associated abnormalities did not need to be considered. The
appearance of this lesion made it unlikely to be a dermoid cyst. Even though
the high fat content in dermoid cysts might present with a similar appearance,
only inflammation would result in contrast enhancement. Lymphoma would present
as a hypointense signal mass on T1- and as a hyperintense signal mass on
T2-weighted MR images; however, the T2-weighted hyperintensity is known to
vary. Wegener's granulomatosis, sarcoidosis, and other inflammatory
pseudotumors could not be excluded from the differential diagnosis because of
their varying appearances on CT and MR imaging. An intraorbital abscess is
usually hypointense on T1- and hyperintense on T2-weighted MR images and
enhances after administration of IV contrast material. However, the clinical
presentation would also commonly aid in the diagnosis of abscess. Metastases
to the orbit are hypointense on T1- and hyperintense on T2-weighted MR images,
with the exception of melanoma. Metastases from melanoma have a hyperintense
signal on T1-weighted MR images and a hypointense signal on T2-weighted MR
images because of their melanin content.
The unique feature of this metastatic lesion is its hypointense signal on
both T1- and T2-weighted MR images. Only a single reported orbital metastasis
from a small-bowel carcinoid tumor has been shown to have a similar appearance
[8]. Thus, when one deals with
an intraorbital mass with the imaging appearance we have described, the
differential diagnosis should also include an islet cell tumor metastasis.
Acknowledgments
We thank Angela Balzé for her assistance in
manuscript preparation.
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Introduction
Case Report
