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Riedel’s thyroiditis and F18-FDG-PET scan
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A 45-year-old woman presented to the ED for worsening dysphagia and right lower anterior neck pain with increasing dyspnea on exertion. She had no prior history of thyroid disease or autoimmune disease and reported no prior head and neck radiation.
Her family history was remarkable only for a brother with a thyroid cyst. On exam, a 5-cm, very hard, nonmobile mass was palpated in the right inferior thyroid lobe. The mass was painful to exam with radiation of the pain to her right jaw.
Initial laboratory evaluation showed a normal thyroid-stimulating hormone of 0.55 µIU/mL, total thyroxine of 8.6 µg/dL, total triiodothyronine of 85 ng/dL and calcitonin less than 2 pg/mL. Anti-thyroid peroxidase and anti-thyroglobulin antibody titers were not elevated.
Stephanie L. Lee
Mass surrounding carotid artery
A CT scan of the neck showed a hypodense 5.5-cm mass that could not be separated from the right thyroid gland (Figure 1). The mass surrounded the proximal right common carotid artery and displaced and narrowed the right internal jugular vein.
The differential diagnosis for this mass included an anaplastic thyroid carcinoma, sclerosing variant of Hashimoto’s disease, sclerosing variant of papillary carcinoma, lymphoma, poorly differentiated thyroid cancer, parathyroid carcinoma, sarcoma or Riedel’s thyroiditis. A core biopsy of the mass showed dense fibrous tissue with a dispersed infiltrate of predominantly small lymphoid cells and scattered plasma cells. No granuloma or carcinoma was seen.
Immunoperoxidase studies revealed positive staining of the lymphoid cells for light chain with a marked predominance of staining of the T-cell antigen (CD3) and only occasional B cells (CD20). There was weak positive staining of plasma cells for CD138 with polyclonal staining for kappa and lambda light chain immunoglobulins. The stain for cytokeratins (SE1/3) and CD30 were negative. There were a few scattered p53 positive cells.
DNA extracted from paraffin blocks showed no rearrangement of the immunoglobulin heavy chain gene or the T-cell receptor gene.
Riedel’s thyroiditis
These results are consistent with an inflammatory/reactive process and not a lymphoproliferative disorder or an infiltrating carcinoma. An F-18 fluorodeoxyglucose (FDG) PET scan showed intense FDG avidity in the right thyroid mass without increased uptake in the remainder of the thyroid (Figure 2).
Figure 1. Axial CT scan of the neck with contrast. A mass is seen in the right lobe of the thyroid. The border between the mass (yellow circle) and the thyroid is not well demarcated. Contrast enhances the normal thyroid gland (THY), but not the mass. The trachea (TR) is deviated to the left without narrowing. The right carotid artery (c) is surrounded by the mass and narrowed compared with the left carotid artery. The right jugular vein (JV) is compressed compared with the left jugular vein.
Images reprinted with permission from Stephanie L. Lee, MD, PhD, ECNU.
The differential decreased to lymphoma, anaplastic/poorly differentiated thyroid cancer and Riedel’s thyroiditis. Lymphoma is usually associated with a long history of chronic thyroiditis and older age. Both lymphoma and anaplastic/poorly differentiated thyroid cancer were eliminated by the core biopsy.
Riedel’s thyroiditis was confirmed after a wedge biopsy of the right lobe, and isthmusectomy was performed because of worsening shortness of breath and tracheal compression. The pathology showed dense lymphoplasmacytic infiltrates and sclerosis with extrathyroidal extension into skeletal muscle. No thyroid malignancy was noted. Immunohistochemical profile was the same as the core biopsy and supported the diagnosis of Riedel’s thyroiditis.
Riedel’s thyroiditis has an incidence of 1 in 100,000 and occurs three to four times more often in women than in men, with a peak incidence from age 30 to 50 years. Thyroid autoantibodies are positive in about 45% of patients. Approximately 25% to 30% of patients are hypothyroid, and 4% are thyrotoxic. These thyrotoxic patients have a low radioactive iodine uptake, likely due to thyroid destruction by the Riedel’s thyroiditis, release of thyroid hormone and suppression of TSH.
Riedel’s thyroiditis is a fibrotic process of the thyroid that extends outside the thyroid into surrounding tissues and obliterates tissue planes. There is a mononuclear lymphocytic infiltrate with plasma cells and prominent IgA-producing cells. This fibrotic process is part of a systemic multifocal fibrosclerosis. Approximately 20% of patients with Riedel’s thyroiditis also had fibrosclerosis in nonthyroidal areas within 10 years of the diagnosis. Riedel’s thyroiditis should be differentiated from paucicellular anaplastic thyroid cancer that typically shows evidence of infarction, necrosis, atypical spindle cells and immunoreactivity for epithelial markers (keratin) and p53.
Imaging of Riedel’s thyroiditis shows decreased contrast enhancement on CT scan and MRI compared with the normal contrast enhancement of the thyroid (Figure 1). Riedel’s thyroiditis is diffusely hypoechoic on ultrasound exam without increased vascular flow by Doppler. Thyroiditis has intense F18-PET-FDG uptake. Hashimoto’s shows diffuse uptake throughout the thyroid while the uptake is focal to the Riedel’s thyroiditis (Figure 2).
Figure 2. Coronal images of CT scan with contrast (A) and F18-FDG-PET scan (B). The CT scan shows the mass with relatively poor contrast enhancement causes deviation of the trachea (TR) to the left. The mass surrounds the right carotid artery (CA). The Riedel’s thyroiditis, but not the normal thyroid gland (THY), is hypermetabolic indicated by an intense F18-FDG uptake (B). The brain is relatively hypermetabolic and uses only glucose as an energy source.
Images reprinted with permission from Stephanie L. Lee, MD, PhD, ECNU.
Treatment options
The best treatment for this rare disease with spontaneous remissions is not known. Options include high-dose glucocorticoid therapy, such as prednisone 80 mg to 100 mg daily with a taper to 10 mg in 5 to 6 months. It is unclear which clinical or imaging parameters might indicate when therapy should be stopped.
Similar to one other case, the resolution of PET uptake in our patient predicted remission of this disease and allowed successful cessation of prednisone therapy after 45 weeks. This patient has been disease-free for 60 months.
Tamoxifen (10 mg to 20 mg twice daily) has been shown in small case studies to decrease Riedel’s inflammation. Tamoxifen may work by stimulating transforming growth factor beta, which can inhibit the fibroblastic proliferation. There are no careful controlled studies of prednisone or tamoxifen alone or in combination because of the small numbers of patients and fluctuation of the clinical course with unexpected remission of the fibrotic process.
Complete surgical removal of the thyroid is not possible because of the extension of the fibrosclerosis beyond the thyroid and obliteration of tissue planes, but partial thyroidectomy/isthmusectomy may be effective in cases of tracheal compression in patients with severe shortness of breath or dyspnea on exertion.
References:
- de Lange WE, et al. Q J Med. 1989;72:709-717.
- Drieskens O, et al. Clin Nucl Med. 2002;27:413-415.
- Few J, et al. Surgery. 1996;120:993-998.
- Hay ID. Mayo Clin Proc. 1985;60:836-843.
For more information:
- Stephanie L. Lee, MD, PhD, ECNU, is an Associate Professor of Medicine and Associate Chief, in the Section of Endocrinology, Diabetes and Nutrition at Boston Medical Center. Lee can be reached at Boston Medical Center, 88 E. Newton St., Endocrinology Evans 201, Boston, MA 02118; email: stephanie.lee@bmc.org.
Disclosure:
- Lee reports no relevant financial disclosures.