Ectopic Thyroid Tissue Masquerading as a Functional Carotid Body Paraganglioma

Abstract

<jats:sec><jats:title>Objective:</jats:title><jats:p> Ectopic thyroid tissue (ETT) is a rare entity resulting from thyroid gland dysembryogenesis. We present a case of ETT confirmed by histopathology that was misdiagnosed clinically as a carotid body tumor. </jats:p></jats:sec><jats:sec><jats:title>Methods:</jats:title><jats:p> A 34-year-old female with a history of thyroidectomy for a goiter presented with 1 year of worsening tachycardia (heart rate ranging from 82 to 111 beats per minute), anxiety, hot flashes, and intolerance to heat. For further evaluation, we obtained imaging of her neck, including a thyroid ultrasound, a computed tomography (CT) scan, and an octreotide scan. We also performed laboratory studies including fractionated 24-hour urine meta-nephrines and thyroid function tests. </jats:p></jats:sec><jats:sec><jats:title>Results:</jats:title><jats:p> Her thyroid ultrasound showed a mass at the right carotid bifurcation, which was confirmed on CT as well as on an octreotide scan. Her free thyroxine was 0.6 ng/dL (normal, 0.7 to 1.5 ng/dL) and her thyroid-stimulating hormone was 4.51 mIU/L (normal, 0.45 to 4.5 mIU/L). Her fractionated 24-hour total urine metanephrines were 1,502 mcg/24-hour (normal, 149 to 535 mcg/24-hour). She underwent resection of a vascular mass from the carotid bifurcation. Histologic examination revealed ETT with dilated follicles filled with colloid with no evidence of paraganglioma/carotid body tumor. </jats:p></jats:sec><jats:sec><jats:title>Conclusion:</jats:title><jats:p> The somatostatin receptor is typically present in paragangliomas; however, there are reports of octreotide uptake within thyroid goiters. It has been demonstrated that psychoactive medications can increase urine metanephrines. Given the patient's psychiatric history and that no other tumors were identified on imaging, it was felt that the elevated urine normetanephrine in this case was most likely due to psychoactive medication use. This case demonstrates the preoperative imaging findings and postoperative pathologic confirmation of an unusual presentation of ETT. </jats:p></jats:sec>

Ectopic thyroid tissue presenting as a carotid body paraganglioma

“…4 There have been only six previously reported cases of ETT at the carotid bifurcation. 5,9,[12][13][14][15] Other unusual locations of ETT include the mediastinum, chest and abdomen. 12 The clinical presentation of our patient was similar to those in previously reported cases -namely, a slow-growing asymptomatic mass.…”

“…5,9,[12][13][14][15] Other unusual locations of ETT include the mediastinum, chest and abdomen. 12 The clinical presentation of our patient was similar to those in previously reported cases -namely, a slow-growing asymptomatic mass. However, on retrospective review it was noted that our patient's preoperative CT scan identified a thyroid gland located in the normal orthotopic position.…”

“…However, uptake of octreotide and 68Ga-DOTATATE within thyroid goitres, and in a case of ETT, has also been reported. 12,17 Albeit rare, ETT is an important differential to consider given the risk of irreversible hypothyroidism. Others have highlighted the importance of combined investigations such as CT, MRI, scintigraphy (somatostatin receptor, technetium-99 or iodine-131) and fine needle aspiration cytology to give a higher sensitivity and specificity when investigating a lateral anterior triangle neck mass.…”

“…Others have highlighted the importance of combined investigations such as CT, MRI, scintigraphy (somatostatin receptor, technetium-99 or iodine-131) and fine needle aspiration cytology to give a higher sensitivity and specificity when investigating a lateral anterior triangle neck mass. 4,12,16 • Ectopic thyroid tissue presenting at the carotid bifurcation is a rare phenomenon and may clinically mimic carotid body tumours. • Lateral ETT typically arises due to dysembryogenesis of the lateral anlage.…”