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Riedel's thyroiditis is a rare disease characterized by chronic fibrosis. Clinical performance of this disease is dense stony goiter, which can poorly be displaced during palpation. The overgrowth of the goiter can lead to the development of compression syndrome. To diagnose we need to made fine needle biopsy and made the final diagnose according to its results or according to the morphological description of the postoperative material. An important step in the diagnosis of Riedel's thyroiditis is the determination of serum IgG and IgG4 to exclude an IgG4-associated disease. Treatment of this disease includes drug therapy, which is based on glucocorticosteroids administration or surgical treatment when develops compression syndrome. This article presents a clinical case of a patient with Riedel's thyroiditis; the main complaints were associated with the growth of goiter and the development of compression syndrome. In this regard, patient underwent surgery on the thyroid gland, and after this we get final diagnose. Due to feeling unwell, drug therapy with glucocorticosteroids was prescribed, against the background of which we noted a positive trend.

Patients with IgG4-related disease (IgG4-RD) are diagnosed in Japan by comprehensive or organ-specific diagnostic criteria. To date, organ-specific criteria have been established for several organs, but not for the thyroid. We attempted to establish diagnostic criteria for IgG4-related thyroid disease (IgG4-RTD) based on IgG4-RD research by The Research Program on Intractable Diseases from the Ministry of Health, Labour and Welfare of Japan. These criteria have been publicly reported to members of both the Japan Endocrine Society and the Japan Thyroid Association. Thyroid diseases associated with IgG4 include Hashimoto's thyroiditis, Graves' disease and Riedel's thyroiditis. As a comprehensive definition that includes both systematic and organ-specific forms, we use the broad term 'IgG4-related thyroid disease'. Diagnostic criteria for IgG4-RTD comprise the following five items: I) enlargement of the thyroid, II) hypoechoic lesions in the thyroid by ultrasonography, III) elevated serum IgG4 levels, IV) histopathological findings in the thyroid lesion (IgG4+ plasma cells >20/HPF and IgG4+/IgG+ plasma cell ratio >30%) and V) involvement of other organs. "Definitive" diagnosis of IgG4-RTD is made when I, II, III and IV are all fulfilled, while "probable" diagnosis of IgG4-RTD is when I, II, and IV or V are fulfilled. Patients who fulfill I, II and III criteria are considered as "possible" IgG4-RTD. We believe that the proposed diagnostic criteria contribute to more accurate diagnosis of IgG4-RTD as well as exclusion of mimicry. Furthermore, they may lead to better understanding of the clinical implications and underlying pathogenesis of IgG4-RTD.

Objective Riedel's thyroiditis (RT) is a very rare chronic fibrosing thyroiditis that is often associated with multifocal fibrosclerosis. Although the relationship of RT and IgG4-related disease (IgG4-RD) has been suggested, the expression of IgG and IgG4 in thyroid tissues of patients with RT has seldom been studied. Design A case series and literature review. Patients and measurements We searched our hospital's pathology database and identified five cases of RT between 2000 and 2019. The expression levels of IgG4 and IgG in thyroid tissues were detected by immunohistochemistry. We also performed a literature search of the electronic databases PubMed/MEDLINE, Web of Science and China National Knowledge Internet (CNKI). Eight papers were included in this study. Results According to immunohistochemistry, the numbers of IgG4+ plasma cells per high-power field (HPF) of the five RT patients at our hospital were 80, 8, 50, 10 and 22, and the respective IgG4+/IgG+ ratios were 76%, 80%, 43%, 19% and 28%. In the literature, 15 RT patients with confirmed IgG4 and IgG immunohistochemical findings were identified. Only seven of them fulfilled the IgG4-RD diagnostic criteria in terms of immunohistochemistry (IgG4+ > 10/HPF, IgG4+/IgG+ > 40%). In order to ensure that most RT cases can meet the IgG4 immunohistochemical criteria, an organ-specific cut-off value (≥10 IgG4+ plasma cells/HPF and ≥ an IgG4+/IgG ratio of 20%) was finally selected in our study. Conclusion Our findings of IgG4 expression in patients with RT suggest that a cut-off of 10 IgG4+ plasma cells/HPF and an IgG4+/IgG ratio of 20% are more suitable diagnostic criteria for RT in IgG4-RD.

Riedel's thyroiditis is a rare inflammatory process which not only involves thyroid gland but also the surrounding vital structures. It may also be associated with various forms of systemic fibrotic disorders. The exact etiology is not known, but currently, the most favored view is that of a localized form of the systemic fibrotic process. We report a case of Riedel's thyroiditis in a male patient, highlighting diagnostic challenges and a rare presentation of hypocalcemia and mimicking thyroid lymphoma. Clinical knowledge of such a presentation of Riedel's thyroiditis would enhance our ability to make a speedy diagnosis. Apart from avoiding aggressive surgical intervention, awareness of such a clinical entity may avoid complications and hence morbidity. Our case also highlights the difficulty in histological diagnosis which is vital to rule out malignancy and avoiding any major surgical intervention fraught with complications. Although the patient had a poor tolerance to Tamoxifen and Rituximab, however, his response to high dose steroids is the currently accepted treatment of choice. This case adds to the sparse literature available on the cytological diagnosis of RT and highlights the diagnostic challenge due to suspicious radiology findings., Highlights • Riedel's thyroiditis, a rare form of chronic thyroiditis is associated with a fibrotic process involving the thyroid gland, leading to anatomical and physiological consequences. • Riedel's thyroiditis is part of the spectrum of IgG4-related systemic disorders (IgG4-RSD). • Clinicians should be aware of RT to differentiate this condition from other thyroid disorders, especially malignant lesions. • Thyroidectomy is indicated for patients with compressive symptoms, suspicion of malignancy and failure of medical management.

Riedel's thyroiditis is a rare form of thyroiditis. Estimated prevalence is 1.06/100,000 population and is reported in 0.05% of thyroidectomy specimens. It has 38% association with systemic fibrotic conditions. We retrospectively reviewed 6 cases of Riedel's thyroiditis at a tertiary care centre in south India, from 2011 through 2019 with special emphasis on demography, clinical presentation, workup, management, intraoperative findings, postoperative outcomes and follow up. There were 4 females and 2 males of which we reported a rare presentation in paediatric age group which was probably never reported before. Presenting symptoms included dysphagia and compressive symptoms in neck. 5 out of 6 cases underwent surgical management- 4 total thyroidectomy and 1 hemithyroidectomy. Postoperative complications noted were temporary hypoparathyroidism, unilateral vocal cord palsy and temporary bilateral vocal cord palsy One case was medically managed with oral corticosteroids. There was no evidence of extra cervical fibrosis on follow up in all patients. There was no cause-specific mortality, and the fibrotic process stabilized or resolved in all patients. Riedel's thyroiditis is a fibroinflammatory disorder presenting with compressive symptoms mandating surgical intervention mainly decompression in the form of isthmectomy. However since extensive interventions are associated with complications it is less favoured approach. Long term follow up of these cases are necessary for detecting evidence of extra cervical fibrosis.

Riedel’s thyroiditis is a rare entity consisting of a fibrotic process of the thyroid which can generate gland destruction, infiltration of cervical structures and even airway obstruction. It has been associated with systemic fibrotic disorders, autoimmune diseases, and more recently with spectrum of diseases related to excess of Immunoglobulin G type 4 (IgG4). Two cases of Riedel’s thyroiditis by IgG4, confirmed by immunohistochemistry and was managed surgically with favorable results during the follow-up time, are presented. These case descriptions highlight the diagnostic challenge of this disease, describe the response with surgical management, and make a brief update on the subject.

Background : Riedel's thyroiditis (RT) is a rare fibrosclerotic disease that affects the thyroid gland and surrounding tissues. The etiology is unknown, and it rarely affects the elderly.Case Presentation : A 56-year-old man, with no particular medical history, was seen in consultation at the Surgery Department of the Treichville Teaching University Hospital for a painless swelling of the anterior base of the neck. Physical examination showed a patient with inspiratory dyspnea probably due to tracheal compression. The patient underwent a subtotal thyroidectomy because of the clinical symptomatology and the persistence of dyspnea. Macroscopically, the thyroid mass was well-encapsulated, weighed 80g, and measured 10 cm x 5 cm x 2 cm. After section, we observed whitish fibrous nodules associated with pinkish-brownish band. Histologically, the architecture of thyroid tissue was restructured by dense and diffuse collagenous fibrosis in which rare atrophic thyroid vesicles were found. The fibrous areas were infiltrated by inflammatory elements, including lymphocytes, plasmocytes, and eosinophilic polynuclear cells. No malignant cells were found. Masson's trichrome staining confirmed the fibrous nature of the thyroid tissue, which is essential for the certain diagnosis of Riedel's thyroiditis. There was no postoperative complication Conclusion : Riedel's thyroiditis is a rare disease that is difficult to diagnose preoperatively despite advances in imaging and fine needle cytology screening methods. Histological examination of the sample confirms the diagnosis of Riedel's thyroiditis. Thyroidectomy is indicated in patients with compression symptoms. Clinicians should suspect Riedel's thyroiditis in patients with a hard thyroid mass with compressive symptoms, despite its rarity.

A hard, palpable mass localized in the perithyroidal soft tissue is often suposed of having a cancerous process. Along with dysphagia or neck pain, it causes patient and physician concern. It is important for a correct diagnosis to differentiate the disease with another with an identical clinical manifestation - a Riedel's thyroiditis. In Riedel's thyroiditis fibrosclerotic organ manifestations can either be a part of IgG4-related disease or solely be located in the thyroid and adjacent tissues and elevation of serum IgG4 can be found.

Acute and chronic thyroid diseases are the most frequently detected disorders being second only to diabetes mellitus.The World Health Organization points out that thyroid diseases’ incidence tends to grow every year. The present paper consists of clinical practice guidelines that consider etiology, clinical course, diagnostics and treatment of acute and chronic inflammatory thyroid diseases (except those of autoimmune type).The clinical practice guidelines provide an important working tool for clinicians including specialty physicians and medical experts. Containing structured and concise information on the specific nosology, diagnostic methods and treatment tips these guidelines allow medical specialists to quickly resolve difficulties and choose the most efficient and personalized treatment (following strict principles of evidence-based medicine at the same time).The clinical practice guidelines were drawn up by highly-skilled professional team of specialty physicians approved by the Expert Council of Russian Federation’s Health Department. These guidelines contain the most complete and up-to-date information required to diagnose acute and chronic thyroiditis, provide patient care and treatment.The working group publishes the present paper in the professional journal dealing with endocrinology topics to improve healthcare quality and refine treatment of acute and chronic thyroiditis (autoimmune thyroiditis excluded). It is advisable to acquaint as many endocrinology and general (family) medicine specialists as possible with the full text of these clinical guidelines.

Idiopathic retroperitoneal fibrosis is a rare fibro-inflammatory disease that can be associated with other IgG4-related diseases (IgG4-RDs). It is exceedingly uncommon to encounter this condition in a patient with Riedel's thyroiditis (RT), another disease in the IgG4-RD family. We present the case of a 53-year-old man with a history of RT who presented for severe localized lower abdominal and suprapubic pain due to obstructive uropathy from extensive retroperitoneal fibrosis. The biopsy of the mass demonstrated fibro-inflammatory tissue, and its immunohistochemistry was notable for IgG4-positive plasma cells. This case highlights the challenge associated with the diagnosis and management of this rare manifestation of IgG4-RD. In a patient with a history of any form of IgG4-RDs, providers should be vigilant for any signs or symptoms that suggest the development of fibrosis in other organs.

Patient: Female, 69-year-old Final Diagnosis: Riedel thyroiditis Symptoms: Dysphagia • goiter Medication: — Clinical Procedure: — Specialty: Endocrinology and Metabolic Objective: Rare disease Background: Riedel’s thyroiditis is a rare form of immunoglobulin G (IgG) 4-related invasive fibrosis of the thyroid gland; given its scarce incidence, standardized therapeutic guidelines are unavailable. Although complications are unusual, obstructive symptoms produced by the stony-hard goiter may put patients’ lives at risk. The diagnosis must be biopsy-proven, and treatment consists of thyroid hormone replacement and anti-inflammatory drugs, although sometimes thyroidectomy may be required. Case Report: A 69-year-old woman presented with a 7-month history of progressive hypothyroidism and obstructive dysphagia. On physical examination, she had a large, stony-hard goiter. A Doppler ultrasound study revealed a massive, avascular enlargement of the thyroid gland. A computed tomography scan failed to demonstrate any extrathyroidal extension of the abnormal tissue. A Tru-Cut biopsy of the thyroid was performed. Extensive replacement of thyroid follicles by prominent bands of fibrous tissue was observed, with follicular obliteration and mild focal occlusive phlebitis. A lymphoplasmacytic infiltrate was clearly identified; no oxyphilic nor giant cells were found. On immunohistochemistry, the immunoglobulin G (IgG) 4/IgG ratio in the plasma cell infiltrate was 40%; increased serum IgG4 levels were also found, supporting the diagnosis of Riedel’s thyroiditis. The patient was successfully treated with levothyroxine replacement and tamoxifen with prompt resolution of obstructive symptoms. Conclusions: Fibrous thyroiditis should be considered in the differential diagnosis of primary hypothyroidism in a patient with a stony-hard goiter. Although steroids are often used as a therapeutic strategy for this disease, our patient had an excellent therapeutic response to tamoxifen, avoiding adverse effects associated with steroid therapy, the higher cost of monoclonal antibody therapy, and surgery-associated risks.

Background: Riedel’s thyroiditis is a rare thyroid pathology which presents a challenge for clinicians to diagnose and treat. Etiology remains largely unknown, although data suggests an association with Hashimoto thyroiditis, systemic fibrosis, and IgG-4 related systemic disease. Presentation of Riedel’s thyroiditis can mimic malignant thyroid neoplasm, lymphoma, or a fibrous variant of Hashimoto thyroiditis. Due to its rarity, there is no consensus on the treatment. Clinical case: A 36-year old woman presented with a two-month history of gradually progressing neck swelling. She developed associated neck pain, decreased range of motion, hoarseness, and dysphagia, without difficulty breathing. One year prior to presentation, she had been diagnosed with hypothyroidism. She did not have a family or personal history of thyroid malignancy, however, she lived near Chernobyl during her childhood. On exam, the anterior and lateral neck was hard and enlarged, but nontender. The neck range of motion was diminished. The initial ultrasound of the thyroid demonstrated asymmetrically enlarged heterogenous diffusely nodular right thyroid and isthmus measuring 1.9cm. A CT of the chest with contrast showed diffusely enlarged thyroid extending superiorly beyond the image with mild tracheal displacement. Initial laboratory results included TSH of 17.40 uU/ml (ref: 0.35-4.94 uU/ml), free T4 of 1.06 ng/dl (ref: 0.61-1.82 ng/dl). She had a significantly increased thyroid autoantibodies (Anti-TPO >700 IU/ml with ref: 0.0-9.0 IU/ml, Anti-TG >2000 IU/ml with ref: 0.0-4.0 IU/ml). PTH and calcium were normal, and calcitonin was low. In the interim, the patient was evaluated by ENT without evidence of airway compromise. She underwent a core biopsy of the right thyroid lobe which demonstrated dense fibrous connective tissue mixed with mature lymphocytes. Pathology and immunostaining results were suggestive of Riedel’s thyroiditis. The patient was started on prednisone 60mg daily, which she tolerated for 6 weeks. Due to side effects, prednisone dose was titrated down and tamoxifen was added. Over the following 6 months, compressive symptoms resolved, and the ultrasound showed a significant decrease in the thyroid size. TSH normalized with thyroid hormone replacement. To date, she is asymptomatic and continues on tamoxifen and low dose prednisone without evidence of progression. Conclusion: Riedel’s thyroiditis is a rare condition that can progress into a medical emergency and should be suspected in patients presenting with a thyroid mass. Clinical awareness of Riedel’s symptomatology and laboratory findings should enhance our ability to distinguish and make the diagnosis. Instituting effective treatment that results in the improvement of symptoms and reduction in thyroid size can be challenging due to possible poor response or development of side effects.

Immunoglobulin-G4-related disease (IgG4-RD) is a chronic immunomediated pathology of different organs of local or systemic nature, which has been established as a separate clinical entity in the early 2000s and is characterized by storiform fibroid inflammation of the affected tissues, their increase, and elevated serum immunoglobulin-G4 (IgG4) levels. The most common manifestations of the disease are major salivary and lacrimal gland enlargement, lymphadenopathy and type 1 autoimmune pancreatitis (AIP1), however, other organs may be also involved (the thyroid, eyes, meninges, heart, lungs, kidneys, aorta, upper airways, mesentery, etc.). The effectiveness of treatment of IgG4-RD, as well as other pathological conditions, is also determined by the timely diagnosis. However, the latter is complicated due to the variety of clinical manifestations and rather variable diagnostic criteria. It is necessary to constantly update the evidence-based knowledge and diagnostic algorithms within this pathology in order to overcome the difficulties, and involve immunologists, endocrinologists, pathologists and specialists in other spheres. This review provides information about the etiology, pathogenesis, and current methods of diagnosis and treatment of IgG4-related diseases, as well as examples of some manifestations of IgG4-RD that an endocrinologist may face in practice.

We present a rare case of Riedel’s thyroiditis in a 78-year-old male, native of hilly region of Nepal who presented with chief complaint of long standing swelling of the thyroid with discharging sinus. Right hemithyroidectomy with excision of sinus was done. Gross examination showed asymmetrically enlarged right lobe of thyroid with adherent fibroadipose and muscular tissue. Microscopy revealed diffuse hyalinised fibrosis of the thyroid parenchyma with presence of variable number of atrophic to few normal thyroid follicles in between. The stroma showed dense lymphoplasmacytic infiltration with foci of calcifications and hemorrhage. There was extension of fibrosis beyond the thyroid capsule, encasing the skeletal muscle bundles at many places. Diagnosis of Riedel’s thyroiditis was made.Riedel’s thyroiditis is a rare entity but can occasionally be encountered. Various imaging modalities may not be helpful for the definite diagnosis. Diagnostic thyroidectomy should be performed for the accurate diagnosis and further management. DOI: 10.21276/APALM.1392

Various thyroid diseases are associated with autoimmunity. Major autoimmune thyroid diseases are Graves' disease (GD) and Hashimoto's thyroiditis (HT). Thyrotropin receptor is an autoantigen in GD, and its immunogenicity has been examined. Immune-checkpoint inhibitor (ICI) is recently widely used for treatment of malignant tumors, but cases of thyroid diseases during ICI treatment have been increasing. Thyroid diseases during ICI therapy have been investigated in immunological and clinical aspects, and their Japanese official diagnostic guidelines were established. In addition, serum and tissue immunoglobulin-G4 levels have been examined in association with clinicopathological characteristics in GD, HT, and Riedel's thyroiditis. We review these diseases associated with thyroid autoimmunity and comprehensively discuss their potential application in future research and therapeutic options.

Background: Riedel’s thyroiditis is an extremely rare condition characterized by an overgrowth of inflammatory fibrosis that destroys the thyroid follicular architecture. The presentation can mimic malignancy, and due to its rarity, the diagnosis can be delayed. Experience with treatment of this condition is limited, but glucocorticoids and tamoxifen have both been shown in case reports to be effective. Clinical Case: A 68 year old woman presented with dyspnea and weakness. Her exam showed a diffusely enlarged thyroid with a hard texture. Labs showed hypothyroidism for which she was started on levothyroxine, and imaging revealed a goiter with a dominant 3.1cm left thyroid nodule causing tracheal narrowing. Laryngoscopy showed R vocal fold paralysis. FNA of this nodule was non-diagnostic; therefore a core biopsy was attempted which showed no thyroid tissue but skeletal muscle and sclerotic fibro-connective tissue infiltrated by chronic inflammatory cells. Neck CT done 1 month after initial presentation showed a diffusely enlarged and heterogeneous thyroid gland encasing the R carotid artery, infiltrating the peri-thyroidal fat, and causing tracheal narrowing. Given ongoing concern for malignancy, she had open incisional thyroid biopsy showing dense fibrous tissue with chronic inflammation and entrapped skeletal muscle, but again no thyroid tissue was identified. Pathology was believed to be consistent with Riedel’s thyroiditis. She was started on prednisone 60mg daily with improvement in her symptoms, and the steroids were gradually tapered off after 9 months of treatment given stable imaging. The patient remained off steroids and without new symptoms for 1.5 years. She was then admitted for syncope and had further evidence of disease progression on CT scan, with continued growth of the mediastinal component as well as encasement of the bilateral internal carotid arteries, right brachiocephalic trunk, trachea, and upper esophagus. Repeat biopsy again showed dense fibrous tissue with scattered small lymphocytes and plasma cells. She was started back on prednisone 60 mg daily, and imaging done after 3 months of treatment showed shrinkage of the size of the neck and mediastinal mass. However, the patient was noted to have Cushingoid features, including moon facies and weight gain. Therefore, tamoxifen 10mg twice a day was started, and the glucocorticoids were successfully tapered off. To date, she remains asymptomatic without evidence of disease progression while on tamoxifen 10mg twice a day. Conclusion: Riedel’s thyroiditis is a rare chronic inflammatory disease characterized by an invasive fibrotic process that can mimic malignancy. Treatment with glucocorticoids and/or tamoxifen can result in improvement in symptoms and reduction of the size of the mass.

Riedel's thyroiditis is a rare form of chronic thyroiditis, predominantly characterized by a fibrotic process associated with mononuclear cell inflammation that classically extends beyond the thyroid into the perithyroidal soft tissue. It can occur in association with Hashimoto's thyroiditis, with elevated serum antithyroid antibody concentrations and lymphocytic infiltration seen in thyroid FNA. We report a case of 53-year-old Caucasian female patient with a clinical history of slowly growing painless multinodular goiter. The patient was referred to the Endocrinology department where physical examination revealed a non-suspicious diffusely enlarged goiter. An ultrasound guided fine-needle aspiration biopsy of the dominant nodule (2 cm in size) was performed, and cytologic findings were suggestive of chronic inflammatory process, with intense lymphocytic infiltration. Hypothyroidism and elevated serum thyroid peroxidase antibody (692 U/mL) were detected in blood work-up and hormone replacement therapy ensued. The diagnosis of Hashimoto's thyroiditis was then established ant the patient was discharged to the general practitioner. Four years after this diagnosis the patient complained of severe flank and lower abdominal pain and returned to our hospital. Abdominal CT scan identified a retroperitoneal periaortic and periureteral mass causing ureteral obstruction and acute renal failure. Amongst other diagnostic tests concurrently excluding malignant or infectious disease, CT scan guided biopsy was performed and revealed retroperitoneal fibrosis with vasculitis and hyaline rings surrounding small retroperitoneal vessels and nerves. Serum IgG4 was negative and erythrocyte sedimentation rate was marginally elevated. Whole body CT scan confirmed mediastinal diffuse fibrosis. Cervical ultrasound showed heterogeneous hypoechoic lesions infiltrating perithyroid muscles and a thyroid biopsy showed dense, hyalinized fibrous tissue that contained few lymphocytes, plasma cells, and eosinophils and almost no thyroid follicles, confirming the diagnosis of Riedel’s thyroiditis. Phospho-calcium metabolism disorders were excluded. Empiric therapy with Tamoxifen 10 mg daily and glucocorticoids was initiated. One-year follow-up imaging indicated disease stabilization. This case portraits the diagnostic challenge of clearly differentiating Riedel’s and Hashimoto’s thyroiditis in the same patient, as the results of imaging, laboratory and cytology studies are often similar. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

Introduction: Thyroid swellings are one of the most common encountered endocrinological presentations however the prevalence of malignancy is about 4-6.5%. Hodgkin lymphomas usually present as neck swelling in form lymphadenopathy and Hodgkin disease affecting the thyroid gland is extremely rare (1-2.5% of all lymphomas). It usually occurs in middle age and has predilection for female gender. It can pose a diagnostic challenge with the histology of sclerosing fibrosis mimicking Riedel’s thyroiditis; another rare cause of stony hard goitre. Case History: A 39yr old female presented with rapidly enlarging painful thyroid mass. She complained of mild dysphagia but denied to have dyspnoea, dysphonia wheeze or stridor. There was no history of weight loss, B symptoms or any significant past illness. Clinically and biochemically she was euthyroid with normal TSH 0.73mU/l(0.35-3.50), Free thyroxine 13pmol/L (8-21), Free T3 3.9pmol/L (3.8-6.0). Blood count showed mild neutrophilia 8.21 (2-7x109/L). IGG subclasses 1-4 were all with normal limits. Initial Ultrasonography demonstrated 4.6 X 3.6cm U3 thyroid nodule extending retrosternally. FNA x2 was THY. Core biopsy demonstrated dense core of fibrous tissue with crushed aggregates of mature lymphoid cells and mixed neutrophils and histiocytes in keeping with fibro inflammatory process suggestive of Riedel’s thyroiditis. Patient was initiated on Prednisolone 100mg OD by the ENT surgeons after MDT discussion and patient had some symptomatic improvement in pain but no discernible reduction in size. Due to side effects from steroids she was referred to endocrinology department. Tamoxifen 20mg BD was started for symptom management. CTNCAP was organised to rule out lymphoproliferative disorder which was negative barring the known thyroid mass. She had no response to Tamoxifen either hence she underwent surgical resection. Surgical resection deemed very difficult due to mass infiltrating the strap muscles and neck vasculature hence wedge resection of the isthmus was done. Histology now revealed bands of dense fibrous tissue with admixed large lymphoid cells showing enlarged, red nucleoli. Immunohistochemistry of the large atypical lymphoid cells expressed CD30, CD15, MUM1, PAX5, CD20, CD79a and BCL6 and diagnosis was revised to Classic Hodgkin lymphoma, nodular sclerosis subtype. She was then referred to haematologist who initiated ABVD chemotherapy and her latest FDG PET scan shows complete metabolic response with significant reduction in the thyroid mass to 17mm X16 mm. Conclusion: Primary thyroid lymphoma can mimic Riedel’s and other forms of fibrosing thyroiditis. Most lymphomas arise from Hashimoto’s thyroiditis. Stony hard neck swellings are difficult to FNA and even core biopsy may not reveal the diagnosis, hence surgical resection and histological diagnosis should be sought earlier as most lymphomas respond well to chemotherapy.

Introduction: Riedel’s thyroiditis (RT) is a fibro-inflammatory process that can affect the thyroid gland alone or might extend to adjacent tissues. This condition may evolve to multifocal systemic fibrosclerosis in 30–40% of the patients. Riedel’s thyroiditis is a rare disease that is usually treated by surgery as it consists of a hardened, adhered goiter with local invasion that resembles a malignant lesion. This thyroid disease is considered the most associated to immunoglobulin G4-related disease (IgG4-RD). IgG4-RD is characterized by a dense lymphoplasmacytic infiltrate with numerous IgG4 positive plasma cells present in other organs besides the thyroid. Case Report: The report refers to a 53-year-old female Brazilian patient. The patient had a medical history of hypothyroidism and also showed increase of the cervical volume since the beginning of 2018. A surgical treatment was proposed in 2019 and histological aspects suggested the diagnosis of RT. After further analysis of the material obtained in biopsy, the microscopy assessment revealed lymphoplasmacytic inflammation with high fibrosis suggesting IgG4 related sclerotic disease. Conclusion: This case highlights the importance of investigating IgG4-RD in patients with RT as it seems to be a new clinical entity. The diagnosis is a challenge and the combination of histopathological features/immunohistochemical staining with clinical, laboratorial, and radiological findings is extremely important.

SummaryRiedel's thyroiditis is a rare type of chronic thyroiditis, associated with fibroinflammatory process and invasion into surrounding tissues, leading to compressive symptoms. A 45-year-old man had a left thyroid mass, presenting with hypotension and bradycardia many times. He was diagnosed with vasovagal reflex caused by cervical vessel compression due to a thyroid lesion. We performed the emergency operation, and most of the left thyroid was removed to relieve the compression on cervical vessels. The result of pathology proved to be Riedel's thyroiditis. The vasovagal reflex did not occur any more during the 28-month follow up, except on the 3rd day after the surgery. Six months after the thyroidectomy, the patient was found to have retroperitoneal fibrosis, diagnosed by biopsy during a laparotomy for biliary disease. Riedel's thyroiditis can lead to a vasovagal episode and might not be a primary thyroid disease but rather a manifestation of the systemic disorder, multifocal fibrosclerosis.

Riedel's thyroiditis (RT) is a rare disorder characterized by extensive fibrosis extending to the extrathyroidal tissues. An elderly male presented with diffuse moderate thyromegaly and hoarseness of voice for two years. Radiology showed extrathyroidal extension around trachea with compression and deviation suggestive of malignancy. Thyroid was hard and non tender. Ultrasound guided Fine Needle Aspiration (FNA) from multiple foci on both sides using thinner needle yielded moderately cellularity showing follicular cells, lymphoplasmacytic infiltrate, scant colloid and fibrous tissue fragments. Hurthle cells were absent. Adiagnosis of chronic thyroiditis was given with possibility of RT in view of clinical and radiological findings. A core biopsy showed similar picture as cytology. Guided FNA from multiple foci using thinner needle helped to obtain adequate material allowing a confident diagnosis. This case adds to the meagre literature available on the cytologic diagnosis of RT and highlights the diagnostic challenge due to suspicious radiology findings.

Riedel’s thyroiditis (RT) represents one type of IgG4-related thyroid disease (IgG4RTD) and the diagnosis involves quantitative immunohistochemistry showing dense lymphoplasmacellular inflammatory infiltrate consisting of IgG4-positive plasma cells with storiform fibrosis and obliterative phlebitis. We report a case of RT with progressive enlargement of the anterior neck, severe dysphagia, odynophagia, and dyspnea. The patient underwent surgical decompression of the airway, protection tracheotomy, and gastrostomy for nutritional intake 6 months after first symptoms. Complete resolution occurred after surgical treatment combined with prednisolone. Immunostaining revealed IgG4-positive plasma cells 12/HPF (high-power field) and the IgG4/IgG ratio 25%, values that were disproportionate to the intensity of the patient’s symptoms. As to this case and the few cases described and analyzed in the literature, our impression is that there is no relation between the intensity of symptoms in RT with the total number of IgG4-positive plasma cells and the IgG4/IgG ratio, but more studies are needed.

This case report reviews the rare condition of Riedel’s thyroiditis via a patient case. The report highlights the difficulties that one may encounter when managing such a case in regards to patient symptoms, side effects of medications and the relapsing nature of the condition. The case report also highlights novel treatment in the treatment of Riedel’s thyroiditis, rituximab, how this works and the resolution of symptoms that we have achieved with our patient on this treatment. Learning points: Riedel’s thyroiditis is characterised by chronic inflammation, which causes dense fibrosis in the thyroid gland. Riedel’s thyroiditis can present with neck pain, dysphagia and dyspnoea with a firm, non-tender mass found on examination. Riedel’s thyroiditis is part of the IgG4-related systemic disorders. Rituximab is a monoclonal antibody that works against the protein CD20. Background This case is important as it highlights the difficulties in managing complex Riedel’s thyroiditis patients. The case also highlights the novel use of rituximab in the treatment of a patient with complex refractory Riedel’s thyroiditis. As this is a rare condition, this case will provide information to readers on the success we have had with this treatment and shed light on the mechanism by which rituximab works.

IgG4-related disease is a newly identified syndrome characterized by high serum IgG4 levels and increased IgG4-positive plasma cells in involved organs. The incidence of IgG4-related thyroiditis in the Caucasian population of Europe is unknown. We investigated formalin-fixed thyroid gland samples of 216 patients (191 Hashimoto's thyroiditis, 5 Riedel's thyroiditis, and 20 goiters, as controls), morphologically, and immunohistochemically. Cases were divided into two groups: IgG4-related Hashimoto's thyroiditis (24 cases) together with Riedel thyroiditis (1 case) and 171 non-IgG4-related thyroiditis. Compared to the non-IgG4-related cases, IgG4-related thyroiditis showed a higher IgG4/IgG ratio (0.6 vs. 0.1, p 0.0001), a higher median IgG4 count (45.2 vs. 6.2, p 0.0001), an association with younger age (42.1 vs. 48.1 years, p = 0.036), and a lower female-to-male ratio (11:1 vs. 17.5:1). Fibrous variant of Hashimoto's thyroiditis was diagnosed in 23 of the 24 IgG4-related cases (96 %) and in 13 of 167 (18 %, p 0.001) non-IgG4-related cases. The single case of IgG4-related Riedel's thyroiditis also showed a higher median IgG4 plasma cell count (56.3 vs. 14.3) and a higher IgG4/IgG ratio (0.5 vs. 0.2) than the four cases of non-IgG4-related Riedel's thyroiditis. Our data suggests the incidence of IgG4-related disease (IgG4-RD) of the thyroid gland in Europe is considerably lower than that observed in other studies. A significant elevation of IgG4-positive plasma cells was only found in a small group of Hashimoto's thyroiditis and then accompanied by intense fibrosis, indicating an association with IgG4-RD. Morphologically, IgG4-RD of the thyroid gland differs from that in other organ systems, exhibiting a dense fibrosis without intense eosinophilia or obliterative phlebitis.

Riedel's thyroiditis (RT) is a rare chronic fibrosing disorder characterized by a hard, infiltrative lesion in the thyroid gland, which is often associated with multifocal fibrosclerosis. Immunoglobulin G4-related disease (IgG4-RD) is typified by infiltration of IgG4-positive plasma cells into multiple organs, resulting in tissue fibrosis and organ dysfunction. In order to evaluate the clinicopathological features of RT and its relationship with IgG4-RD, we performed a Japanese literature search using the keywords "Riedel" and "Riedel's thyroiditis." We used the electronic databases Medline and Igaku Chuo Zasshi, the latter of which is the largest medical literature database in Japan. The diagnosis of RT was based on the presence of a fibroinflammatory process with extension into surrounding tissues. Only 10 patients in Japan fulfilled RT diagnostic criteria during the 25-year period between 1988 and 2012. Two patients with confirmed IgG4/IgG immunohistochemical findings demonstrated 43 and 13 IgG4-positive plasma cells per high-power field, respectively, and the IgG4-positive/IgG-positive plasma cell ratios of 20% and less than 5%. Of the 10 patients with RT, two received glucocorticoids, one of whom experienced marked shrinkage of the thyroid lesion. One patient had extra-thyroid involvement in the form of retroperitoneal fibrosis. Although the clinicopathological features of RT suggest that IgG4-RD may be the underlying condition in some cases, further investigation is needed to clarify the etiology of RT in relation to IgG4-RD.

Background Riedel's thyroiditis (RT) is a rare form of chronic thyroiditis, associated with fibroinflammatory process involving the thyroid and surrounding cervical tissues, leading to compressive symptoms. Case presentation We present a case of RT in a 73-year-old female with dyspnoea caused by severe trachea compression. She had reported dyspnoea during physical stress, and had noticed a large mass on the front of the neck. Despite the combination of various imaging modalities, the thyroid mass was not differentiated from thyroid malignancy and other thyroid disorder. Total thyroidectomy and tracheotomy were performed. During surgery, the thyroid had severe adhesion to surrounding tissue and the pathology revealed RT. Conclusions Clinicians should be aware of RT. It is important to differentiate this condition from other thyroid disorders, especially malignant lesions. Thyroidectomy is indicated for patients with compressive symptoms, suspicious malignancy and failure of conservative management., Highlights • Riedel's thyroiditis (RT) is a rare form of chronic thyroiditis, associated with fibroinflammatory process involving the thyroid and surrounding cervical tissues, leading to compressive symptoms. • It is important to differentiate this condition from other thyroid disorders, especially malignant lesions. • Thyroidectomy is indicated for patients with compressive symptoms, suspicious malignancy and failure of conservative management. • Clinicians should be aware of RT.

IgG4-related disease is a set of symptoms resulting from a chronic, usually multiple organ inflammatory condition which affects various organs. It consists of lymphoplasmacytic infiltrations with attendant fibrosis and deep vein thrombosis. Frequently observed tissue lesions are accompanied by elevated IgG4 levels in serum. The etiopathogenesis of the lesions is of multifactor character and the clinical manifestation of the disease is highly diverse. The diagnostic process is based on the patient’s medical history, clinical examination and additional tests, including a histopathological examination of the infected organ’s tissues. Almost forty different locations of the disease have been reported, including disorders of the endocrine system. IgG4-related endocrinopathies are quite rare. However, it is likely that the diagnosis is under-reported due to lack of awareness of this clinical entity. Despite increasing interest in the subject, there are not enough reliable studies evaluating the link between IgG4-RD and endocrine disorders.

A 39 year old female presented with rapidly enlarging goitre, minimal obstructive symptoms and no constitutional symptoms. Clinical examination revealed diffusely enlarged, firm, non-tender thyroid gland. Biochemical investigations showed subclinical hypothyroidism, positive thyroid antibodies and unremarkable inflammatory markers. Ultrasound examination and CT scan of the neck were suspicious of Riedels thyroiditis. The patient was referred for a FDG PET scan to evaluate for systemic fibro-inflammatory process or lymphoma. Subsequent core biopsy of the thyroid gland demonstrated a chronic inflammatory process with fibrosis consistent with Riedels thyroiditis. A FDG PET/CT study showed diffuse FDG uptake in the thyroid gland and no abnormal retroperitoneal FDG uptake elsewhere to suggest active retroperitoneal fibrosis. The goitre reduced in size with thyroid hormone replacement and steroids, however the patient was lost to follow up.Otuz dokuz yaşında bir kadın hasta, hızlı büyüyen bir guatr tablosu, minimal obstrüktif belirtiler ile başvurdu. Ek yakınmaları yoktu. Fizik muayenede tiroid bezi diffüz olarak büyümüş, sert ve ağrılı idi. Biokimyasal tetkiklerde subklinik hipotiroidi ve positif tiroid antikorları saptanırken inflamasyon belirteçleri yüksek değildi. Ultrason ve boyun BT görüntüleme tetkikleri Riedel tiroiditini düşündürmekteydi. Hasta, sistemik bir fibro-inflamatuvar hastalık ya da lenfoma yönünden değerlendirilmek üzere FDG PET görüntülemeye yönlendirildi. Bunu takiben yapılan tiroid bezi biyopsisi Riedel tiroiditi ile uyumlu olan, fibrozisin eşlik ettiği kronik inflamatuvar bir süreci gösterdi. FDG PET/BT incelemesi tirod bezinde diffüz artmış FDG tutulumunu gösterirken, aktif retroperitoneal fibrozu düşündürecek anormal bir retroperitoneal FDG tutulumu mevcut değildi. Tiroid hormon replasmanı ve steroidlerle guatr boyutu küçültüldü, ancak hastanın ileri takipleri yapılamadı.

A 44-year-old female presented with a two-month history of a neck mass, sore throat, hoarseness, and intermittent dysphagia. Examination revealed a “woody” hard swelling arising from the right lobe of the thyroid. Clinically this was felt to be classical Riedel’s thyroiditis (RT). Thyroid ultrasound showed a diffusely enlarged, low echogenicity thyroid with a multinodular goitre. An abnormal nodule extending across the isthmus was noted. Following a nondiagnostic fine needle aspiration, an open core biopsy was performed. This showed dense sclerotic fibrosis punctuated by nodular mononuclear inflammatory cells, which obscured follicular epithelial cells consistent with a fibrosing thyroiditis (Riedel’s thyroiditis). A biopsy of pretracheal lymph nodes showed a sclerotic process throughout the lymph nodes and nests of epithelium bands with squamous differentiation obscured by a fibrous process. These findings raised the differential diagnosis of diffuse sclerosing variant of papillary thyroid carcinoma (DSV-PTC) with metastasis to lymph nodes. A total thyroidectomy and pretracheal lymph node dissection were performed. The final histological diagnosis was DSV-PTC. When managing a patient with presumed RT it is important to consider malignancy in the differential. DSV-PTC is one of the more aggressive forms of thyroid cancer but with early diagnosis and appropriate treatment patients may have excellent outcomes.

A 42-year-old woman presented with a rapidly enlarging right-sided thyroid mass and underwent hemithyroidectomy. Riedel's thyroiditis was only diagnosed upon surgical decompression of the right carotid artery 2 years later. She became more symptomatic as Riedel's thyroiditis progressed, and mediastinal fibrosclerosis developed over the next 12 months. Oral prednisolone failed to improve her condition, and she was commenced on tamoxifen. Despite initial improvement, her symptoms recurred 2 years later, mainly arising from compression of the trachea and esophagus at the thoracic inlet. Fluorodeoxyglucose positron emission tomographic scan showed locally advanced active invasive fibrosclerosis in the neck and mediastinum. An elevated activin-A level of 218 pg/mL was consistent with active inflammation. IgG subtypes (including IgG4) were normal. Two courses of iv methylprednisolone were given but only produced transient improvement. Subsequently, the patient received 3 doses of i.v. rituximab at monthly intervals and had prompt sustained symptomatic improvement. Activin-A level decreased to 122 pg/mL 10 months after rituximab therapy. Fluorodeoxyglucose positron emission tomographic scan 6 weeks after therapy showed reduction in inflammation. A further scan at 10 months demonstrated ongoing response to rituximab. This is a case of refractory Riedel's thyroiditis with symptomatic, biochemical, and radiological improvement that has persisted 14 months after rituximab. The likelihood and duration of response to rituximab in Riedel's thyroiditis requires further study.

Context IgG4-positive (+) plasma cells have been reported in both Riedel's thyroiditis (RT) and Hashimoto's thyroiditis (HT). These cells are the hallmark of IgG4-related disease (IgG4-RD). Objective We sought to determine whether RT is part of IgG4-RD spectrum. Design, setting and patients This was a case-control study performed at a tertiary medical centre. We included RT cases from the period 1958 to 2008 that had sufficient paraffin-embedded tissue for IgG4 immunostaining. Controls were patients with HT, age and gender matched, with similar pathology criteria. Main outcome measure The main outcome measures were the intensity of the IgG4 staining and the clinical and histological correlates with IgG4-RD. Results Six pairs of RT and HT were analysed. The mean age was 44·7 years. In both groups, 5/6 cases had positive IgG4 staining. The mean number of IgG4 + cells/ HPF, normalized to the degree of inflammation, was 3·2 ± 3·0 SD (RT) vs 0·9 ± 0·7 (HT), P = 0·15, for fibrotic areas and 2·1 ± 2·3 SD vs 1·0 ± 0·8 (P = 0·39) for areas with lymphoid aggregates. We found the number of IgG4 + cells in RT to be inversely correlated with the duration of disease (P = 0·046). Three RT cases had associated comorbidities from the IgG4-RD spectrum while none of the HT cases had such conditions. Conclusions Riedel's thyroiditis is a component of IgG4-RD with the density of the IgG4 + lymphocytic infiltrate being time dependent. In this small study, we did not identify differences in IgG4 infiltration between RT and HT, minimizing the utility of this marker in RT diagnosis.

Riedel’s thyroiditis is a rare inflammatory process which not only involves thyroid gland but also the surrounding vital structures. It may also be associated with various forms of systemic fibrotic disorders. The exact etiology is not known, but currently most favored view is that of a localized form of systemic fibrotic process. We report a case of Riedel’s thyroiditis in a patient, highlighting a rare presentation mimicking anaplastic carcinoma. Clinical awareness of such presentation of Riedel’s thyroiditis would enhance our ability to make this diagnosis promptly. Apart from avoiding or minimizing aggressive surgical intervention, awareness of such clinical entity may avoid complications and hence morbidity. Our case also highlights the difficulty in histological diagnosis which is very important to rule out malignancy and avoiding any major surgical intervention fraught with complications. Good response to high dose steroids as seen in our case is the current accepted treatment of choice.

This article describes an unusual case of Riedel's thyroiditis and discusses its imagery, pathology, and treatment.

This review article deals with the classification, clinical features and morphology of thyroiditis. These inflammatory diseases account for approximately 20 % of all thyroid diseases. The vast majority of cases of thyroiditis are of immunogenic origin while non-immunogenic thyroiditis (caused by pathogens or iatrogenic) is a rarity.

Background Riedel thyroiditis is a rare, chronic inflammatory disease of the thyroid, characterized by a dense fibrosis that replaces normal thyroid parenchyma. In literature descriptions of individual cases of Riedel thyroiditis can be found. Case report We present an euthyroid patient with multinodular goiter who was diagnosed with Riedel thyroiditis using pathology. Imaging diagnostic methods (Ultrasonography, X-ray computed tomography, Magnetic resonance imaging, Radionuclide imaging) or various tests of thyroid function cannot confirm the diagnosis of Riedel thyroiditis. Conclusion Only level of IgG4 may be helpful for the diagnosis of Riedel thyroiditis, while pathology is used for its definitive confirmation.

Riedel's thyroiditis, known as invasive fibrous thyroiditis, is a very rare form of chronic thyroiditis. It is hard to make the diagnosis without surgical biopsy. We present a case of Riedel's thyroiditis in a 52-year-old female with past history of Hashimoto's thyroiditis. She suffered from bilateral neck pain, which radiated to both lower jaws. The erythrocyte sedimentation rate was 125 mm/hour. Subacute thyroiditis superimposed on Hashimoto's thyroiditis was diagnosed and treated with steroid. However the response was poor and she had a history of severe peptic ulcer. To avoid inducing the peptic ulcer by steroid, she received bilateral subtotal thyroidectomy. During surgery, the thyroid had severe adhesion to surrounding soft tissue and the pathology showed Riedel's thyroiditis. The neck pain improved after thyroidectomy. Tamoxifen has been given for 8 months and the size of remnant thyroid decreased to 8 mm. We concluded that combined thyroidectomy and tamoxifen successfully cured a patient with Riedel's thyroiditis.

Riedel's thyroiditis is an extremely rare disease that is difficult to diagnose correctly using preoperative diagnostic tools because it can mimic malignant neoplasm or the fibrous variant of Hashimoto thyroiditis during preoperative physical, radiologic, and pathologic examination. We describe here a rare case of Riedel's thyroiditis in an elderly patient and its radiologic characteristics.

Riedel's thyroiditis (RT) is a rare inflammatory disease that results in fibrosis of the thyroid gland and invasion to the surrounding structures of the neck. Follicular adenoma (FA) of the thyroid is the most common benign neoplasm of the gland.A 42-year-old woman was referred to the outpatient clinic due to a multinodular goiter and thyroiditis. The patient was euthyroid and thyroid function tests were within normal limits. Thyroid antibodies (thyroid peroxidase antibody and thyroglobulin antibody) were high. Thyroid ultrasonography showed multiple iso-hypoechoic nodules and thyroiditis. Fine-needle aspiration cytology was performed, and it was consistent with 'suspicious for a follicular neoplasm' according to the Bethesda system. Due to the clinical findings, which included weight loss and sweating, and the cytological results indicative of a follicular neoplasm, the patient underwent a total thyroidectomy. The histopathological diagnosis was RT associated with FA. The patient was started on thyroid hormone (thyroxine) replacement therapy after surgery and was evaluated for additional fibrosis related to RT.To our knowledge, this is the first case of RT associated with FA in an asymptomatic patient with a multinodular goiter and high thyroid antibodies reported in the literature.

Context: Riedel's thyroiditis is a rare inflammatory process involving the thyroid and surrounding cervical tissues and is associated with various forms of systemic fibrosis. Riedel's presentation is complex, including a thyroid mass associated with local symptoms, characteristic biochemical abnormalities such as hypocalcemia and hypothyroidism, as well as the involvement of a wide range of other organ systems. Diagnosis of Riedel's thyroiditis requires histopathological confirmation, but due to high complication rates, the role of surgical intervention is limited to airway decompression and diagnostic tissue retrieval. Unique among processes of the thyroid, Riedel's is commonly treated with long-term antiinflammatory medications to arrest progression and maintain a symptom-free course. Due to its rarity, Riedel's may not be immediately diagnosed, so clinicians benefit from recognizing the constellation of findings that should make prompt diagnosis possible. Evidence Acquisition: A review of print and ele...

Invasive fibrous thyroiditis (IFT) is the rarest form of thyroiditis, and reports are often limited to case reports and small case series. In this study, we aimed to summarize our institutional experience with IFT since 1976.We retrospectively reviewed the cases of all patients with IFT evaluated at Mayo Clinic, Rochester, Minnesota, from 1976 through 2008, with special emphasis on clinical presentation, associated risk factors, associated comorbid conditions, complications, and treatment.Twenty-one patients met our inclusion criteria of (i) IFT confirmed by pathologic review at our institution and (ii) evidence of extension of fibrosis outside the thyroid capsule. Most patients (17, 81%) were women (mean age, 42 years). Presenting symptoms included pain (24%), dysphagia (33%), vocal cord paralysis (29%), and tracheal narrowing (48%). Three patients had associated hypoparathyroidism. Sixteen (76%) had a history of tobacco use, and 10 (48%) were current smokers. Fibrosing mediastinitis was present in four, orbital fibrosis in one, retroperitoneal fibrosis in three, and pancreatic fibrosis in one (38% had extracervical fibrotic processes). Eighteen patients had partial thyroidectomy, 7 (39%) of whom had surgical complications involving vocal cords and parathyroid. Two required tracheostomy. Thirteen had corticosteroid therapy; six received tamoxifen. There was no cause-specific mortality, and the fibrotic process stabilized or partially resolved in all patients.IFT often is associated with a systemic extracervical fibrotic process and tobacco use. Attempted thyroid resection often results in postoperative complications. Long-term follow-up showed no deaths from IFT and showed stability of the thyroiditis.

It is about 100 years since the publication of the original description of the disorder now termed as Hashimoto's thyroiditis (HT) or Hashimoto's disease. Hashimoto's thyroiditis has been commonly considered as a well-defined clinicopathological entity, characterized by the presence of goiter and serum thyroid autoantibodies. Very recently, new studies have reported that there is a unique subtype of HT, termed as immunoglobulin (Ig)G4 thyroiditis, which is characterized by lymphoplasmacytic infiltration, fibrosis, increased IgG4-positive plasma cell in the thyroid and high IgG4 level in the serum. Furthermore, from a clinical aspect, IgG4 thyroiditis presents significantly different characteristics from non-IgG4 thyroiditis, with IgG4 thyroiditis being more closely associated with rapid progress, subclinical hypothyroidism, higher levels of circulating antibodies and more diffuse low echogenicity. This review will introduce the most recent concepts about etiologic mechanisms, clinical, imaging and laboratory features of HT and its histological characteristics. Especially, recent advances in recognizing HT with special reference of IgG4-related sclerosing disease (IgG4-RSD) will be summarized. Furthermore, the differences and close relationship between HT and Riedel's thyroiditis (RT), which was also demonstrated to be involved in IgG4-RSD spectrum, will be reviewed.

Objective Riedel's thyroiditis is a chronic fibrosing disorder of unknown etiology often associated with “multifocal fibrosclerosis.” IgG4-related systemic disease is characterized by IgG4+ plasma cell infiltration and fibrosis throughout many organs. We hypothesized that Riedel's thyroiditis is part of the IgG4-related systemic disease spectrum. Methods We searched our institution's pathology database using the terms “Riedel's,” “struma,” “thyroid,” and “fibrosis,” and identified 3 cases of Riedel's thyroiditis. Riedel's thyroiditis was diagnosed if there was a fibroinflammatory process involving all or a portion of the thyroid gland, with evidence of extension of the process into surrounding tissues. Immunohistochemical stains for IgG4 and IgG were performed. The histopathologic and immunohistochemical features of each involved organ were evaluated. The clinical features of one patient with multiple organ system disease were described. Results All 3 thyroidectomy samples stained positively for IgG4-bearing plasma cells. One patient had extensive extrathyroidal involvement diagnostic of IgG4-related systemic disease, including cholangitis, pseudotumors of both the lung and lacrimal gland, and a lymph node contiguous to the thyroid that stained intensely for IgG4+ plasma cells. The histologic features of all organs involved were consistent with IgG4-related systemic disease. Patient 3 had 10 IgG4+ plasma cells per high-power field initially, but rebiopsy 2 years later demonstrated no IgG4+ plasma cells. That patient's second biopsy, characterized by fibrosis and minimal residual inflammation, further solidifies the link between IgG4-bearing plasma cells in tissue and the histologic evolution to Riedel's thyroiditis. Conclusion Riedel's thyroiditis is part of the IgG4-related systemic disease spectrum. In many cases, multifocal fibrosclerosis and IgG4-related systemic disease are probably the same entity.

Unusual presentations of thyroid neoplasms have been reported from time to time. Four such cases of bizarre presentations of thyroid malignancies seen in the ENT Department of ESIC Hospital, K.K. Nagar, Chennai, India are presented. These cases highlight certain important issues concerning the diagnosis and management. A review of the literature on the subject is discussed.

The concomitant occurrence of retroperitoneal fibrosis (RF) and Riedel's thyroiditis is reported in two patients, one of whom presented with anuria. The etiology is discussed, and it is concluded that immunological mechanisms with arteritis might be of importance. The associations between Riedel's thyroiditis, RF, mediastinal fibrosis, slcerosing chol-angitis, retroorbital fibrosis and fibrosis in other organ systems are thought to be different manifestations of a so-called multifocal idiopathic fibrosclerosis. The benefical effect of glucocorticoids in early stages of the disease is mentioned.