American Journal of Neuroradiology 21:320-321 (2 2000)
© 2000 American Society of Neuroradiology
ARTICLE
Riedel's Thyroiditis in Multifocal Fibrosclerosis: CT and MR Imaging Findings
Ali Özgen
,a and
Aysenur Cilaa
a From the Department of Radiology, Hacettepe University, School of Medicine, Sihhiye, 06100, Ankara, Turkey.
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Abstract
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Summary: Riedel's thyroiditis is a rare disorder of unknown
etiology and may be seen isolated or as a part of multifocal
fibrosclerosis. It is important to distinguish Riedel's thyroiditis
from thyroid carcinoma. Reports about imaging features of Riedel's
thyroiditis are limited in the radiologic literature. We describe
herein CT and MR imaging features of Riedel's thyroiditis in
a case of multifocal fibrosclerosis with previously unreported
radiologic observations.
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Introduction
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Multifocal fibrosclerosis is a rare syndrome characterized by
fibrosis involving multiple organ systems (
1). Varying combinations
of involvement have been reported: Riedel's thyroiditis, retroperitoneal
fibrosis, orbital pseudotumor, mediastinal fibrosis, and sclerosing
cholangitis (
1–
4). Although it is important to distinguish
Riedel's thyroiditis from thyroid carcinoma, reports about imaging
features of Riedel's thyroiditis are very limited in the radiologic
literature (
5–
8). Herein, we describe imaging features
of Riedel's thyroiditis in a case of multifocal fibrosclerosis
with previously unreported radiologic observations.
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Case Report
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A 46-year-old man presented with dysphagia and hoarseness. Physical
examination revealed an enlarged and hard thyroid gland. Laboratory
findings were remarkable for high levels of alkaline phosphatase
and
-glutamyl transferase. Sedimentation rate was 45 mm/hr.
Sonography demonstrated a symmetrically enlarged and hypoechoic
thyroid. Scintigraphy failed to reveal any uptake in the gland.
CT of the neck showed an enlarged and hypodense thyroid gland
surrounding the trachea posteriorly and compressing the esophagus.
After infusion of contrast medium, most of the thyroid showed
decreased enhancement, whereas a small area in the gland enhanced
normally (
Fig 1A). MR imaging of the neck showed a mass that
was hypointense on T1- and T2-weighted images, replacing most
of the thyroid gland with minimal enhancement after gadolinium
injection (
Fig 1B–D). Anterior to the mass was seen a
small amount of normal thyroid parenchyma with normal intensity
and normal enhancement after gadolinium injection. No abnormal
lymph node was identified in the neck. Fine needle aspiration
biopsy was attempted but could not be performed because of hardness
of the mass. Tru-cut biopsy of the thyroid revealed only dense
fibrous tissue with some inflammatory cells lacking vessels.
No acini were seen. Histopathologic findings were diagnostic
for Riedel's thyroiditis.
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FIG 1. A, Enhanced CT of the neck shows an enlarged and hypodense thyroid gland surrounding the trachea and compressing the esophagus. Note the small piece of normal enhancing thyroid tissue (arrow).
B and C, T1-weighted (560/25/2 [TR/TE/excitations]) unenhanced (B) and fast spin-echo T2-weighted (3800/96/3) (C) MR images of the neck showing the enlarged and diffusely hypointense thyroid gland with a small piece of thyroid tissue with normal intensity (arrow).
D, T1-weighted (560/25/2) MR image after administration of gadolinium shows an extremely diminished enhancement of most of the thyroid gland. Note the anteriorly located normal thyroid tissue with normal homogenous enhancement (arrow).
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Abdominal sonography showed segmental dilatations in the left intrahepatic biliary tract. Abdominal CT confirmed the findings on sonography. Retroperitoneal fibrosis surrounding the abdominal aorta also was noted. Endoscopic retrograde cholangiopancreatography revealed multiple segmental dilatations and strictures in the left intrahepatic biliary tract consistent with sclerosing cholangitis. CT of the thorax and MR imaging of the orbits were within normal limits. The patient was given corticosteroid therapy with the diagnoses of Riedel's thyroiditis, retroperitoneal fibrosis, and sclerosing cholangitis. After 3 months of corticosteroid therapy, dysphagia and hoarseness disappeared; the size of the thyroid gland diminished on palpation; laboratory values became normal; and sonography and CT findings of the liver returned to normal. Follow-up MR imaging of the thyroid revealed no significant change in size or MR characteristics of the mass 6 months later.
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Discussion
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Multifocal fibrosclerosis is a rare syndrome of unknown etiology
characterized by fibrosis involving multiple organ systems (
1).
Retroperitoneal fibrosis, Riedel's thyroiditis, orbital pseudotumor,
mediastinal fibrosis, and sclerosing cholangitis have been reported
to be a part of this syndrome (
1–
4). Isolated reports
of pulmonary fibrosis, fibrous parotitis, fibrosclerosis in
the kidneys and pituitary gland, pancreatic fibrosis, testicular
fibrosis, Dupuytren's contracture, subcutaneous fibrosis, vasculitis,
and neurologic involvement also have been reported.
Riedel's thyroiditis may be seen isolated or as a part of multifocal fibrosclerosis. Its major clinical significance lies in its ability to mimic invasive thyroid carcinoma. Some affected patients benefit from corticosteroid therapy (6–8). On imaging, Riedel's thyroiditis is reported to be homogeneously hypoechoic on sonography and shows hypodense-to-normal thyroid tissue on CT scans (5). Slight enhancement of the mass has been noted after administration of contrast medium (7). Invasion of nearby soft tissues or compression of the trachea or esophagus or a combination of these three characteristics may be observed. Only two case reports have defined MR imaging features of Riedel's thyroiditis. The thyroid was reported to be hypointense on both T1- and T2-weighted images (5, 6), with marked homogeneous enhancement after gadolinium administration (6). Our sonography, unen-hanced CT, and unenhanced MR imaging features were similar to those presented in the literature. We observed, however, a considerably decreased enhancement after gadolinium administration on MR imaging. Decreased enhancement also was observed after administration of iodinated contrast medium on CT, which increased the contrast between the normal thyroid tissue and the fibrotic parenchyma. We think that decreased enhancement after administration of contrast medium was caused by dense fibrosis that replaced most of the thyroid gland and was consistent with extremely diminished vascularity compared with the normal, highly vascular, thyroid parenchyma.
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Conclusion
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We described imaging features of Riedel's thyroiditis in a patient
with multifocal fibrosclerosis. A thyroid hypodense on CT and
hypointense on T1- and T2-weighted MR images can be suggestive
of Riedel's thyroiditis whether invasion to nearby soft tissues
is observed or not. Administration of contrast medium may be
helpful in differentiating the normal thyroid parenchyma from
the fibro-sclerotic mass. To our knowledge, no other entity
causes diffuse decreased enhancement after gadolinium administration
on MR imaging or administration of iodinated contrast medium
on CT. Therefore, these radiologic findings may be diagnostic
for Riedel's thyroiditis.
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Footnotes
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101 Address reprint requests to Ali Özgen, MD, Sporcular Sitesi,
Ilkyerlesim Mahallesi, 438. sokak, No:12, Batikent, 06370, Ankara,
Turkey.
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References
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Received June 14, 1999;
accepted after revision August 20, 2000.
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Abstract
Introduction