Intracardiac ectopic thyroid

Right Ventricular Outflow Tract Obstruction in Adults: A Systematic Review and Meta-analysis

Background

Right ventricular outflow tract obstruction (RVOTO) is a cause of hemodynamic instability that can occur in several situations, including cardiac surgery, lung transplantation, and thoracic surgery, and in critically ill patients. The timely diagnosis of RVOTO is important because it requires specific considerations, including the adverse effects of positive inotropes, and depending on the etiology, the requirement for urgent surgical intervention.

Methods

The objective of this systematic review and meta-analysis was to determine the prevalence of RVOTO in adult patients, and the distribution of all reported cases by etiology.

Results

Of 233 available reports, there were 229 case reports or series, and 4 retrospective cohort studies, with one study also reporting a prospective cohort. Of 291 reported cases of RVOTO, 61 (21%) were congenital, 56 (19%) were iatrogenic, and 174 (60%) were neither congenital nor iatrogenic (including intracardiac tumour). The mechanism of RVOTO was an intrinsic obstruction in 169 cases (58%), and an extrinsic obstruction in 122 cases (42%). A mechanical obstruction causing RVOTO was present in 262 cases (90%), and 29 cases of dynamic RVOTO (10%) were reported. In the 5 included cohorts, with a total of 1122 patients, the overall prevalence was estimated to be 4.0% (1%-9%).

Conclusions

RVOTO, though rare, remains clinically important, and therefore, multicentre studies are warranted to better understand the prevalence, causes, and consequences of RVOTO.

Ectopic thyroid tissue: An unusual cause of intracardiac mass

Intracardiac ectopic thyroid tissue is an extremely rare condition, with only 37 cases reported in the English literature. We present a case of intracardiac ectopic thyroid adenoma and briefly review the published reports.

Incidentally detected ectopic thyroid in juxta cardiac location-Imaging and pathology

Ectopic thyroid gland is a developmental anomaly that results from the arrest of thyroid tissue along its path of descent from the floor of mouth to the pre tracheal position in the lower neck. It is typically found along the thyroglossal duct with the base of the tongue being the most common site. Apart from mediastinal extension of goiter, the incidence of true intrathoracic ectopic thyroid tissue is rare. Presence of ectopic thyroid has been reported not only in the chest but also in the abdomen and pelvis. Pericardial and intracardiac locations are extremely uncommon and right ventricle location is predominant among the described cases. We describe a case of incidentally detected ectopic thyroid tissue in a rarer location-adjacent to the left atrium. The patient, who had undergone a nephrectomy for renal oncocytoma 5 years ago, presented with unintentional weight loss and left sided flank pain, prompting a workup to rule out abdominal malignancy. Findings on the computed tomography (CT) scan of the abdomen and pelvis prompted further investigation including a chest CT which showed a heterogeneously enhancing mass near the left atrium. Given its location, further radiological investigations played an important role in eliminating the differential diagnosis of paraganglioma. The mass was surgically resected and discovered to be a hyperplastic thyroid nodule on histologic examination.

Intrapericardial left-sided ectopic thyroid mass supplied by the left circumflex artery

Intrapericardial left-sided ectopic thyroid tissue is a rare entity. We report a 47-year old female patient with an intrapericardial mass mounting the left atrial wall. Two prominent vessels, both originating from the left circumflex artery (LCX), supplied the tumour. Owing to the compression of the left atrium and the left upper pulmonary vein, the patient was highly symptomatic with exertional dyspnoea and ventricular extrasystoles. Histopathological examination showed regressive thyroid adenoma with no signs of malignancy. Complete resection was feasible. The evaluation of thyroid hormone levels was not indicative for diagnosis. Postoperative hormone substitution appeared to be unnecessary.

Cellular and molecular events on the development of mammalian thyroid C cells

Thyroid C cells synthesize and secrete calcitonin, a serum calcium-lowering hormone. This review provides our current understanding of mammalian thyroid C cells from the molecular and morphological perspectives. Several transcription factors and signaling molecules involved in the development of C cells have been identified, and genes expressed in the pharyngeal pouch endoderm, neural crest-derived mesenchyme in the pharyngeal arches, and ultimobranchial body play critical roles for the development of C cells. It has been generally accepted, without much-supporting evidence, that mammalian C cells, as well as the avian cells, are derived from the neural crest. However, by fate mapping of neural crest cells in both Wnt1-Cre/R26R and Connexin(Cxn)43-lacZ transgenic mice, we showed that neural crest cells colonize neither the fourth pharyngeal pouch nor the ultimobranchial body. E-cadherin, an epithelial cell marker, is expressed in thyroid C cells and their precursors, the fourth pharyngeal pouch and ultimobranchial body. Furthermore, E-cadherin is colocalized with calcitonin in C cells. Recently, lineage tracing in Sox17-2A-iCre/R26R mice has clarified that the pharyngeal endoderm-derived cells give rise to C cells. Together, these findings indicate that mouse thyroid C cells are endodermal in origin.

Coexistence of non-functional ectopic thyroid tissue and a normal thyroid: A case report

The aim of this study was to report a rare case of non-functional ectopic thyroid tissue in the neck with a coexisting normal thyroid. A 36-year-old female presented with a mass in the anterior neck. The thyroid function of the patient was normal. Ultrasonography and computed tomography (CT) revealed a normal thyroid gland and a solid mass in the middle lower neck. Scintigraphy showed a normal thyroid and the mass did show any uptake of ^99mTcO_4^- . The patient underwent en bloc resection. During surgery, the mass was observed to be well encapsulated and completely separated from the thyroid gland. Histology revealed it as ectopic thyroid tissue. The patient had an uneventful recovery.

Ectopic mediastinal goiter successfully managed via cervical approach: case report and review of the literature

BACKGROUND

Ectopic mediastinal goiter is a rare entity that presents diagnostic and treatment challenges to the clinician.

METHODS

A case of primary ectopic mediastinal goiter is presented and use of a cervical approach for excision is described herein. Additionally, precedent literature highlighting surgical treatment approaches is reviewed.

RESULTS

The distinction between primary and secondary ectopic mediastinal goiter is significant as this indicates the vascular supply to the ectopic mass. Previous authors suggested open thoracic procedures for all primary mediastinal goiters to safely divide intrathoracic vascular supply, but favorably positioned anterior mediastinal goiter may be safely removed via cervical approach. This is the second case of primary ectopic mediastinal goiter successfully resected via cervical approach.

CONCLUSION

Select cases of primary mediastinal goiter may be amenable to excision via cervical approach, avoiding potential complications of open thoracic procedures. Additionally, CT-guided biopsy is an effective tool in preoperative diagnosis of anterior mediastinal masses.

Ectopic thyroid tissue in the periaortic area, cardiac cavity and aortic valve in a Beagle dog - a case report

Microscopic examination of the heart of a clinically normal 14-month-old female Beagle dog revealed the presence of ectopic thyroid tissue at the base of the heart, around the aorta, and intracardially at the level of the left ventricle and the aortic valve. The tissue was composed of well-differentiated follicles lined by a cuboidal epithelium and containing colloid. Follicular cells and colloid exhibited strong thyroglobulin immunoreactivity, while no parafollicular cells were noted and the immunoreactions for calcitonin remained consistently negative. Although in the dog ectopic thyroid tumors represent 1-10% of all heart base neoplasms (Capen, 1978; Bracha et al., 2009), to the best of our knowledge, nonneoplastic ectopic thyroid tissue has not been reported in the heart of the dog itself or within the dog aortic valve.

Ectopic thyroid in the aortic valve of a Han Wistar rat

Histological examination of the heart of a clinically normal, 10-week-old female Han Wistar rat revealed a 600 x 400-mum mass of ectopic thyroid tissue within the subendothelial connective tissue of the aortic valve. The mass protruded into the left ventricular lumen and was composed of single layers of cuboidal to low-columnar epithelium organized into follicles often containing colloid. Parafollicular cells were not evident. To the authors' knowledge, this is the first report of intracardiac ectopic thyroid gland in the rat and the first report of ectopic thyroid within a heart valve in a mammal.

Morphogenesis of the thyroid gland

Congenital hypothyroidism is mainly due to structural defects of the thyroid gland, collectively known as thyroid dysgenesis. The two most prevalent forms of this condition are abnormal localization of differentiated thyroid tissue (thyroid ectopia) and total absence of the gland (athyreosis). The clinical picture of thyroid dysgenesis suggests that impaired specification, proliferation and survival of thyroid precursor cells and loss of concerted movement of these cells in a distinct spatiotemporal pattern are major causes of malformation. In normal development the thyroid primordium is first distinguished as a thickening of the anterior foregut endoderm at the base of the prospective tongue. Subsequently, this group of progenitors detaches from the endoderm, moves caudally and ultimately differentiates into hormone-producing units, the thyroid follicles, at a distant location from the site of specification. In higher vertebrates later stages of thyroid morphogenesis are characterized by shape remodeling into a bilobed organ and the integration of a second type of progenitors derived from the caudal-most pharyngeal pouches that will differentiate into C-cells. The present knowledge of thyroid developmental dynamics has emerged from embryonic studies mainly in chicken, mouse and more recently also in zebrafish. This review will highlight the key morphogenetic steps of thyroid organogenesis and pinpoint which crucial regulatory mechanisms are yet to be uncovered. Considering the co-incidence of thyroid dysgenesis and congenital heart malformations the possible interactions between thyroid and cardiovascular development will also be discussed.

Thyroid gland development and function in the zebrafish model

Thyroid development has been intensively studied in the mouse, where it closely recapitulates the human situation. Despite the lack of a compact thyroid gland, the zebrafish thyroid tissue originates from the pharyngeal endoderm and the main genes involved in its patterning and early development are conserved between zebrafish and mammals. In recent years, the zebrafish has become a powerful model not only for the developmental biology studies, but also for large-scale genetic analyses and drug screenings, mostly thanks to the ease with which its embryos can be manipulated and to its translucent body, which allows in vivo imaging. In this review we will provide an overview of the current knowledge of thyroid gland origin and differentiation in the zebrafish. Moreover, we will consider the action of thyroid hormones and some aspects related to endocrine disruptors.

Multinodular goitre in lingual thyroid: case report

Objective:

We report a case of a multinodular goitre developing in a lingual thyroid.

Method:

Case report, and discussion of the embryology and treatment of lingual thyroids.

Case report:

A 66-year-old woman presented with dysphagia secondary to a multinodular lingual goitre. A previously silent lingual thyroid had undergone multinodular change to cause dysphagia and eventually airway compromise. The goitre was excised via a midline, mandible-splitting approach.

Conclusion:

Lingual thyroids have an incidence of one in 3000 to 10 000. There has not previously been a reported case of such an ectopic gland undergoing multinodular changes and presenting in later life.

Intracardiac Ectopic Thyroid Carcinosarcoma in a Dog

A 13-year-old spayed female Labrador Retriever with a 1-year history of progressive exercise intolerance was diagnosed with an interventricular mass in the heart via echocardiogram. The animal's general condition progressively declined over the next 8 months, and it was euthanatized. The intracardiac mass, which protruded into the lumen of the right ventricle, was removed at necropsy and fixed in 10% buffered formalin. Histopathologic diagnosis was an ectopic thyroid carcinosarcoma based on the presence of 3 distinct neoplastic tissue types. Intermixed within the tumor were neoplastic thyroid follicles containing colloid and solid nests of thyroid follicular epithelial cells, vascular channels and clefts filled with blood and lined by neoplastic endothelium, and osteoid surrounded by spindle cells and often rimmed by large multinucleated cells. Immunohistochemical reaction for thyroglobulin was positive in the tumor cells forming the colloid-filled follicles and solid nests of epithelial cells. Neoplastic endothelium was positive for factor VIII-related antigen. The thyroid gland was located in its normal anatomic position and was histologically normal, ruling out the possibility that the intracardiac tumor was a metastatic lesion. To the authors' knowledge this is the first reported case of an intracardiac ectopic thyroid carcinosarcoma, and possibly the first ectopic thyroid carcinosarcoma in any location in any species.

Early developmental specification of the thyroid gland depends on han-expressing surrounding tissue and on FGF signals

The thyroid is an endocrine gland in all vertebrates that develops from the ventral floor of the anterior pharyngeal endoderm. Unravelling the molecular mechanisms of thyroid development helps to understand congenital hypothyroidism caused by the absence or reduction of this gland in newborn humans. Severely reduced or absent thyroid-specific developmental genes concomitant with the complete loss of the functional gland in the zebrafish hands off (han, hand2) mutant reveals the han gene as playing a novel, crucial role in thyroid development. han-expressing tissues surround the thyroid primordium throughout development. Fate mapping reveals that, even before the onset of thyroid-specific developmental gene expression, thyroid precursor cells are in close contact with han-expressing cardiac lateral plate mesoderm. Grafting experiments show that han is required in surrounding tissue, and not in a cell-autonomous manner, for thyroid development. Loss of han expression in the branchial arches and arch-associated cells after morpholino knock-down of upstream regulator genes does not impair thyroid development, indicating that other han-expressing structures, most probably cardiac mesoderm, are responsible for the thyroid defects in han mutants. The zebrafish ace (fgf8) mutant has similar thyroid defects as han mutants, and chemical suppression of fibroblast growth factor (FGF) signalling confirms that this pathway is required for thyroid development. FGF-soaked beads can restore thyroid development in han mutants, showing that FGFs act downstream of or in parallel to han. These data suggest that loss of FGF-expressing tissue in han mutants is responsible for the thyroid defects.

Ectopic Thyroid Gland on the Ascending Aorta with a Partial Pericardial Defect: Report of a Case

Intrathoracic ectopic goiters are rare. To our knowledge, only two reports of thyroid tissue on the aorta have been reported in the English literature. A 42-year-old woman was found to have a right paracardiac mass. Sternotomy revealed a firm and encapsulated tumor attached to the anterolateral surface of the ascending aorta and a defect in the right superior part of the pericardium. The mass was completely excised and histopathologic examination confirmed a multinodular goiter. We discuss the features of this rare tumor.

The 22q11 deletion syndrome candidate gene Tbx1 determines thyroid size and positioning

Thyroid dysgenesis is the major cause of congenital hypothyroidism in humans. The underlying molecular mechanism is in most cases unknown, but the frequent co-incidence of cardiac anomalies suggests that the thyroid morphogenetic process may depend on proper cardiovascular development. The T-box transcription factor TBX1, which is the most probable gene for the 22q11 deletion syndrome (22q11DS/DiGeorge syndrome/velo-cardio-facial syndrome), has emerged as a central player in the coordinated formation of organs and tissues derived from the pharyngeal apparatus and the adjacent secondary heart field from which the cardiac outflow tract derives. Here, we show that Tbx1 impacts greatly on the developing thyroid gland, although it cannot be detected in the thyroid primordium at any embryonic stage. Specifically, in Tbx1-/- mice, the downward translocation of Titf1/Nkx2.1-expressing thyroid progenitor cells is much delayed. In late mutant embryos, the thyroid fails to form symmetric lobes but persists as a single mass approximately one-fourth of the normal size. The hypoplastic gland mostly attains a unilateral position resembling thyroid hemiagenesis. The data further suggest that failure of the thyroid primordium to re-establish contact with the aortic sac is a key abnormality preventing normal growth of the midline anlage along the third pharyngeal arch arteries. In normal development, this interaction may be facilitated by Tbx1-expressing mesenchyme filling the gap between the pharyngeal endoderm and the detached thyroid primordium. The findings indicate that Tbx1 regulates intermediate steps of thyroid development by a non-cell-autonomous mechanism. Thyroid dysgenesis related to Tbx1 inactivation may explain an overrepresentation of hypothyroidism occurring in patients with the 22q11DS.

Heterotopic intrathymic thyroid tissue

Heterotopic intrathymic thyroid tissue is an extremely rare condition, but it is important to distinguish it from metastases of clinically undetected thyroid carcinoma because metastatic papillary thyroid carcinoma is often so well differentiated, simulating normal thyroid tissue. Described herein are histological findings of heterotopic intrathymic thyroid tissue that was incidentally identified in a woman with papillary thyroid carcinoma during histological examination of a radical neck dissection specimen. These findings emphasize that this rare incidence may occur and should be differentiated from metastatic papillary carcinoma. Histologically, the patient's intrathymic thyroid follicles were identical to the normal thyroid follicles, having flat cuboidal cells with uniformly small nuclei without nuclear grooves or inclusions. The follicular cells had a low Ki-67 labeling index close to zero, and immunonegativity for galectin-3, HBME-1, and RET oncoprotein, in contrast to the tumor cells in primary papillary thyroid carcinoma of the patient. To the authors' knowledge this is the first case report of intrathymic heterotopic thyroid tissue posing a diagnostic difficulty in a patient with papillary thyroid carcinoma.

Arteries define the position of the thyroid gland during its developmental relocalisation

During vertebrate development, the thyroid gland undergoes a unique relocalisation from its site of induction to a distant species-specific position in the cervical mesenchyme. We have analysed thyroid morphogenesis in wild-type and mutant zebrafish and mice, and find that localisation of growing thyroid tissue along the anteroposterior axis in zebrafish is linked to the development of the ventral aorta. In grafting experiments, ectopic vascular cells influence the localisation of thyroid tissue cell non-autonomously,showing that vessels provide guidance cues in zebrafish thyroid morphogenesis. In mouse thyroid development, the midline primordium bifurcates and two lobes relocalise cranially along the bilateral pair of carotid arteries. In hedgehog-deficient mice, thyroid tissue always develops along the ectopically and asymmetrically positioned carotid arteries, suggesting that, in mice (as in zebrafish), co-developing major arteries define the position of the thyroid. The similarity between zebrafish and mouse mutant phenotypes further indicates that thyroid relocalisation involves two morphogenetic phases, and that variation in the second phase accounts for species-specific differences in thyroid morphology. Moreover, the involvement of vessels in thyroid relocalisation sheds new light on the interpretation of congenital thyroid defects in humans.

An intracardiac accessory thyroid gland

This report describes a 62-year-old woman with a history of pulmonary embolism who presented with a right ventricular cardiac mass that proved histologically to be normal thyroid tissue. The patient was clinically and biochemically euthyroid. Six months after excision, an iodine-123 whole-body uptake and scan demonstrated no residual ectopic thyroid tissue.

The developing mouse thyroid: Embryonic vessel contacts and parenchymal growth pattern during specification, budding, migration, and lobulation

Normal mouse thyroid development has been revised to identify critical morphogenetic events. The early thyroid primordium associates with the aortic sac endothelium at the time of specification and budding. The vascular contact is lost after the thyroid buds from the pharyngeal endoderm, but is resumed before the gland divides to form two lobes. Lateral expansion of parenchyma takes place along the course of the third pharyngeal arch arteries. Thyroid precursor cells expressing Titf1/Nkx2.1 do not proliferate until the migration stage, implicating that progenitors likely are recruited from outside the thyroid placode. Early lobulation involves engulfment of the entire ultimobranchial bodies by the growing midline thyroid. At the same time, proliferation of the ultimobranchial body epithelium is silenced preceding the differentiation of C cells. Before folliculogenesis, thyroid lobe enlargement is reminiscent of a budding-branching-like growth pattern. It is suggested that thyroid inductive signals arise from embryonic vessels, and that this provides ideas to conceptually new pathogenetic mechanisms of thyroid dysgenesis.

Controversial ectopic thyroid: a case report of thyroid tissue in the axilla and benign total thyroidectomy

A 43-year-old woman presented with a mass in her left axilla, which was surgically excised. Histologically, the tissue was a reactive lymph node with adjacent thyroid follicular tissue. The differential diagnosis included benign ectopic thyroid versus metastatic well-differentiated follicular-derived thyroid carcinoma. Because of the possibility of carcinoma, the patient underwent a diagnostic total thyroidectomy. The thyroid was grossly normal with no histologic evidence of malignancy. Post-operatively, the patient underwent a whole body 131I scan. Aside from an expected residual uptake in the thyroid bed region, there was no extrathyroidal uptake to suggest additional ectopic thyroid tissue or metastatic disease. At the time of this scan, her thyrotropin (TSH) was 92.8 microU/mL, thyroglobulin was less than 0.3 ng/mL, and thyroglobulin antibody was less than 3 IU/mL. Abnormalities in the embryologic development and migration of the thyroid gland can result in ectopic thyroid tissue. The most frequent locations are along the midline from the base of the tongue to the mediastinum. Only rare case reports exist of ectopic thyroid in other locations, including the chest (heart, trachea), abdomen (liver, gallbladder, pancreas), and pelvis (vagina). This case represents the first description of thyroid tissue in the axilla with a histologically benign thyroid gland.

Thyroid development and its disorders: genetics and molecular mechanisms

Thyroid gland organogenesis results in an organ the shape, size, and position of which are largely conserved among adult individuals of the same species, thus suggesting that genetic factors must be involved in controlling these parameters. In humans, the organogenesis of the thyroid gland is often disturbed, leading to a variety of conditions, such as agenesis, ectopy, and hypoplasia, which are collectively called thyroid dysgenesis (TD). The molecular mechanisms leading to TD are largely unknown. Studies in murine models and in a few patients with dysgenesis revealed that mutations in regulatory genes expressed in the developing thyroid are responsible for this condition, thus showing that TD can be a genetic and inheritable disease. These studies open the way to a novel working hypothesis on the molecular and genetic basis of this frequent human condition and render the thyroid an important model in the understanding of molecular mechanisms regulating the size, shape, and position of organs.

Thyroid carcinoma arising from a sacrococcygeal mass: a malignant teratoma?

A 59-year-old African American male with a remote history of Graves' disease presented with a 13-cm sacrococcygeal mass that was resected. Pathologic examination revealed this to be papillary thyroid carcinoma with large areas of hemorrhage and necrosis. No other teratomatous elements were identified. The patient underwent extensive evaluation of the thyroid gland with ultrasound, computed tomography (CT) scan, and laboratory studies without any evidence of thyroid mass or malignancy. In addition, further evaluations with chest/abdominal/pelvic CT as well as a bone scan failed to reveal any evidence of metastatic disease. At 1-year follow-up, the patient has remained euthyroid and without evidence of recurrence. We believe that our patient may represent the first reported case of malignant transformation of mature thyroid tissue in a sacrococcygeal teratoma. The impact of his diagnosis on the decision-making for performing a total thyroidectomy is discussed.

Accessory thyroid gland at carotid bifurcation presenting as a carotid body tumor: case report and review of the literature

Patients with carotid body tumors referred to vascular surgeons usually undergo magnetic resonance imaging (MRI) as part of the workup. We present a case report of a 39-year-old woman with a presumed carotid body tumor, as was expected from clinical and MRI findings. At surgery, the ectopic thyroid tissue was suspected, and resection was performed. Histologic examination showed normal thyroid tissue with no sign of malignancy. Postoperative thyroid analysis showed a normally located, properly functioning thyroid gland. Ectopic thyroid glands are generally found in the midline, as a result of abnormal median migration. Their presence lateral to the midline with a proper functioning thyroid gland in its normal position is extremely rare. Although several submandibular thyroid glands have been reported, a close relation with the carotid arteries was described only once. When MRI scans of a presumed carotid body tumor show tumor characteristics that are not fully specific for a carotid body tumor, the possibility of ectopic thyroid tissue should be entertained, which can be the patient's only properly functioning thyroid tissue. In such cases, additional assessment, including thyroid tests, should be considered before surgery.

Ectopic thyroid gland in the porta hepatis and lingua

A rare case of an ectopic thyroid gland in the porta hepatis and in the tongue in an asymptomatic euthyroid 24-year-old woman is reported. A solitary inhomogeneous, hypoechogenic and hyperechogenic mass in the porta hepatis was accidentally discovered by ultrasonography. Subsequent computed tomography demonstrated a heterogeneous, well-defined tumor with small calcifications without signs of environmental invasion. A hemangioma and focal nodular hyperplasia were excluded by blood pool and hepatobiliary scintigraphy. Surprisingly, fine-needle aspiration cytology revealed normal thyroid tissue. (123)I-scintigraphy confirmed the presence of ectopic dual thyroid tissue in the hepatic porta and lingua. At clinical inspection the lingual thyroid gland was palpable and visible, and appeared solid and spheroidal. The subhepatic, ectopic thyroid mass was resected. Postoperatively, thyroid hormone replacement was started to prevent an enlargement of the lingual thyroid. Today, 4 years after surgery, the patient remains euthyroid.