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Accessory thyroid gland at carotid bifurcation presenting as a carotid body tumor: case report and review of the literature
Accessory thyroid gland at carotid bifurcation presenting as a carotid body tumor: Case report and review of the literature Evert-Jan F. Hollander, MD, Michel J. T. Visser, MD, PhD, and Jary M. van Baalen, MD, PhD, Leiden, The Netherlands 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. (J Vasc Surg 2004;39:260-2.)
DEVELOPMENT OF THYROID GLAND The thyroid gland is the first endocrine gland to appear during embryonic development. It begins to develop about 24 days after fertilization, from a median endodermal thickening in the floor of the primitive pharynx between the first and second branchial arches, just caudal to the future site of the medial tongue bud. This thickening soon forms a down-growth known as the thyroid diverticulum. As the embryo elongates and the tongue grows, the developing thyroid gland descends into the neck, passing ventral to the developing hyoid bone and the lateral cartilages. The developing thyroid gland is connected to the tongue by the thyroglossal duct. The opening of this duct in the tongue is called the foramen cecum. The thyroid diverticulum is first hollow, but soon becomes solid and divides. The right and left lobes are connected by an isthmus that lies anterior to the second and third tracheal rings. By 7 weeks the thyroid gland has usually reached its final site in the neck. By this time the thyroglossal duct has normally degenerated and disappeared. A pyramidal lobe is present in about 50% of persons, and may be attached to the hyoid bone by fibrous or muscular tissue. The pyramidal lobe represents a persistent portion of the inferior end of the thyroglossal duct. The small opening of the thyroglossal duct persists as a small blind pit, the foramen cecum of the tongue. The lateral anlage arises as a diverticulum from the fourth and From the Department of Vascular Surgery, Leiden University Medical Center. Competition of interest: none. Reprint requests: Dr Evert-Jan F. Hollander, Leiden University Medical Center, Department of Vascular Surgery, Albinusdreef 2, Leiden, Zuid 2300 RC, The Netherlands (e-mail: [email protected]). 0741-5214/2004/$30.00 ⫹ 0 Copyright © 2004 by The Society for Vascular Surgery. doi:10.1016/j.jvs.2003.07.018
260
fifth pharyngeal pouches and forms the parafollicular cells, which produce calcitonin.1 ECTOPIC OR ACCESSORY THYROID GLAND Rarely, the thyroid gland fails to descend, resulting in a lingual thyroid gland.2 Very rarely, incomplete descent results in the thyroid gland appearing high in the neck, at or just inferior to the hyoid bone. Accessory thyroid tissue may appear in the tongue or in the neck superior to the thyroid gland. It originates from remnants of the thyroglossal duct, and may be found anywhere from the tongue to the usual site of the thyroid gland (Fig 1). Various extremely rare sites of ectopic thyroid gland have been reported, including submandibular localization. It may then have the same presentation as any other neoplasm of the submandibular space.1 DEVELOPMENT OF CAROTID BODY The carotid body is derived from both mesoderm and elements of the third branchial arch and neural crest ectoderm, but not from endoderm, like the thyroid gland. It is a pinkish gray structure, 3 to 4 mm in diameter, located within the adventitial layer of the posteromedial aspect of the common carotid bifurcation. Tumors arising from this body are called paragangliomas, because they arise from paraganglioma cells. No relationship to development of the thyroid gland is known.3 CASE REPORT A 39-year-old woman with swelling over the right carotid bifurcation was referred to our department with a presumed carotid body tumor. The swelling had been present and asymptomatic for years, with no progression. The family history for carotid body tumor was negative. We found a firm mass, which could be moved laterally but not in the craniocaudal direction, suggestive of
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Hollander, Visser, and van Baalen 261
Fig 2. MRI scan shows a mass (2.8 ⫻ 2.3 ⫻ 3.3 cm) between the internal and external carotid arteries.
Fig 1. Ectopic thyroid gland. 1, Lingual thyroid; 2, intralingual thyroid; 3, thyreoglossus duct cyst; 4, low neck ectopia; 5, thyroid gland, normal position; 6, intratracheal position; 7, mediastinal position.
a mass at the carotid bifurcation. The diameter was approximately 4 cm; there were no signs of cranial nerve dysfunction. Laboratory testing showed no abnormalities. A magnetic resonance image (MRI) showed a mass (2.8 ⫻ 2.3 ⫻ 3.3 cm) between the internal and external carotid arteries. The typical characteristics of a carotid body tumor (homogeneous and highly vascularized mass) were described in the report (Fig 2). Intraoperatively, the tumor did not show the characteristic macroscopic aspect of a carotid body tumor. The suspicion of ectopic thyroid tissue was raised, and the tumor was excised. Histologic analysis showed an encapsulated tumor (4.1 ⫻ 3.0 ⫻ 2.8 cm) consisting of nodular thyroid tissue without any signs of malignancy. Postoperative evaluation with ultrasonography showed a normal thyroid gland in the proper median position. Additional scanning also showed a normal thyroid gland, without any accessory localization. Thyroid function tests yielded normal results. Furthermore, the MRI assessment was revised, which had been misinterpreted. In retrospect, the mass was heterogenous, with no typical vascular pattern. Fig 3 shows a typical MRI of a carotid body tumor.
DISCUSSION Ectopic thyroid tissue is defined as thyroid tissue not located anterolaterally to the second to fourth tracheal cartilages. Since 1869, when Hickmann4 first reported lingual thyroid, several reports of ectopic thyroid tissue have been published. The lingual location is most common,
Fig 3. MRI shows a typical carotid body tumor.
accounting for 90% of reported cases.5,6 Other rare sites of ectopic thyroid gland include the mediastinum,7 esophagus,8 lung,9 heart,10 aorta,11 and abdomen.12-14 In 70% to 80% of cases the ectopic thyroid tissue is the only functional thyroid tissue.4,15,16 The literature contains only 14 reports of ectopic thyroid tissue located in the submandibular region.17-30 The simultaneous finding of submandibular ectopic thyroid tissue and a functional thyroid gland in its proper location is extremely rare. Sambola-Cabrer et al24
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262 Hollander, Visser, and van Baalen
first reported ectopic thyroid tissue in the submandibular location in combination with a normally located but atrophic thyroid gland. A submandibular ectopic thyroid gland with a normally functioning thyroid gland in its proper location has been reported only once.19 In 1988 Rubenfield et al28 reported ectopic thyroid tissue at the carotid bifurcation. In contrast to our case, they did not find a proper functioning thyroid gland in its normal location. Several theories have been postulated to explain the origin of the lateral thyroid gland. Displacement during the course of embryonal development seems a logical explanation. The most accepted hypothesis for ectopic submandibular thyroid tissue in the absence of a normally located thyroid gland might represent dysembryoplasia of the lateral anlage, with nonmigration and agenesis of the median anlage. Nicastri et al31 reported that benign thyroid tissue may also metastasize to the cervical lymph nodes. From the point of view of a vascular surgeon, different causes of neck masses can be confused with carotid body tumors. These include metastatic cancer to the cervical nodes, branchial cleft cyst, and low parotid tumor. It is clear that an accurate preoperative diagnosis of a tumor mass in the neck region is important in clinical management. According to our findings, the possibility of ectopic thyroid tissue, although extremely rare, should also be considered if MRI findings are not completely typical. Standard management, that is, excision biopsy of the neck mass, can lead to irreversible hypothyroid disease, because in most cases it is the only functional thyroid tissue in the body. Careful additional analysis, including the thyroid gland, should therefore be considered preoperatively. In all cases diagnostic excision of the lesion should be performed; however, thyroid function tests can be important for adequate postoperative follow-up of thyroid function. REFERENCES 1. Moore KL. The developing human: clinically oriented embryology. 4th ed. Toronto: W.B. Saunders; 1988. p 184-7. 2. Hazard JB, Smith DE. The thyroid. Baltimore, Md: Williams & Wilkins; 1964. p 26. 3. Dean HD. Carotid body tumors. In: Sabiston DC Jr, editor. Sabiston’s textbook of surgery. 15th ed. Philadelphia: W.B. Saunders; 1997. p 1660. 4. Hickmann W. Congenital tumor of the base of the tongue, pressing down the epiglottis on the larynx and causing death by suffocation sixteen hours after birth. Trans Pathol Soc Lond 1869;20:160-1. 5. Larochelle D, Arcand P, Belzile M, et al. Ectopic thyroid tissue: a review of the literature. J Otolaryngol 1979;8:523-30. 6. Pintar JE, Dominique CTA. Normal development of the hypothalamicpituitary-thyroid axis. In: Braverman LE, Utiger RD, editors. Werner
7. 8. 9. 10. 11. 12.
13. 14. 15. 16. 17. 18.
19. 20. 21.
22. 23. 24. 25.
26. 27. 28.
29.
30. 31.
and Jugbar’s the thyroid. 6th ed. Philadelphia, Pa: Lippingcott; 1991. p 11-4. Arriaga MA, Meyers EN. Ectopic thyroid tissue in the retroesophageal superior mediastinum. Otolaryngol Head Neck Surg 1988;99:338. Whale HL. Esophageal tumor of thyroid tissue. BMJ 1987;2:1921. Simon M, Baczako K. Thyroid inclusion in the lung: metastasis of an occult carcinoma or ectopia? Pathol Res Pract 1989;184:263. Casanova JB, Daly RC, Edwards BS, et al. Intracardiac ectopic thyroid. Ann Thorac Surg 2000;70:1694-6. Williams RJ, Lindop G, Butler J. Ectopic thyroid tissue on the ascending aorta: an operative finding. Ann Thorac Surg 2002;73:1642-3. Gungor B, Kebat T, Ozaslan C, et al. Intraabdominal ectopic thyroid presenting with hyperthyroidism: report of a case. Surg Today 2002; 32:148-50. Shiraishi T, Imai H, Fukutone K, et al. Ectopic thyroid in the adrenal gland. Hum Pathol 1999;30:105-8. Jamshidi M, Kasirye O, Smith DJ. Ectopic thyroid nodular goiter presenting as a porta hepatis mass. Am Surg 1998;64:305-6. Meyerson M, Smith HW. Lingual thyroid: a review. Conn Med 1966; 30:341-4. Noyek AM, Friedberg J. Thyroglossal duct and ectopic thyroid disorders. Otolaryngol Clin North Am 1981;14:187-201. Kumar R, Sharma S, Marwah A, et al. Ectopic goiter masquerading as submandibular gland swelling. Clin Nucl Med 2001;26:306-9. Feller KU, Mavros A, Gaertner HJ. Ectopic submandibular thyroid tissue with a coexisting active and normally located thyroid gland: case report and review of the literature. Oral Surg 2000;90:618-23. Akoz T, Erdogan B, Ayham M, Cinar F. Ectopic submandibular thyroid tissue. Rev Laryngol Otol Rhinol (Bord) 1998;119:323-5. Temmel AF, Baumgartner WD, Steiner E, et al. Ectopic thyroid gland simulating a submandibular tumor. Am J Otolaryngol 1998;19:342-4. Di Benedetto V. Ectopic thyroid gland in the submandibular region simulating a thyroglossal duct cyst: a case report. J Pedriatr Surg 1997;32:1745-6. Sironi M, Assi A, Andruccioli M, Spreafico G. Submandibular ectopic thyroid gland. Clin Nucl Med 1996;21:585. Hansen LT, Christensen PH. Ectopic thyroid gland in the submandibular region. Ugeskr Laeger 1996;158:3324-5. Sambola-Cabrer I, Fernandez-Real JM, Ricart W, et al. Ectopic thyroid tissue presenting as a submandibular mass. Head Neck 1996;18:87-90. Morgan NJ, Emberton P, Barton RP. The importance of thyroid scanning in neck lumps: a case report of ectopic tissue in the right submandibular region. J Laryngol Otol 1995;109:674-6. Latimer J, Lindsay KA. Case report: lingual thyroid in association with lateral ectopic thyroid mass. Clin Radiol 1995;50:501-2. Aguirre A, de la Piedra M, Ruiz R, Portilla J. Ectopic thyroid tissue in the submandibular region. Oral Surg 1991;71:73-6. Rubenfeld S, Joseph UA, Schwartz MR, et al. Ectopic thyroid in the right carotid triangle. Arch Otolaryngol Head Neck Surg 1988;114: 913-5. Alsop JE, Yerbury PJ, O’Donnell PJ, Heyderman E. Signet-ring cell microfollicular adenoma arising in a nodular ectopic thyroid: a case report. J Oral Pathol 1986;15:518-9. Helidonis E, Dokaianakis G, Papazoglou G, et al. Ectopic thyroid gland in the submandibular region. J Laryngol Otol 1980;94:219-24. Nicastri AD, Foote FW Jr, Frazell EL. Benign thyroid inclusions in cervical lymph nodes. JAMA 1965;194:1.
Submitted May 21, 2003; accepted Jul 1, 2003.
DEVELOPMENT OF THYROID GLAND The thyroid gland is the first endocrine gland to appear during embryonic development. It begins to develop about 24 days after fertilization, from a median endodermal thickening in the floor of the primitive pharynx between the first and second branchial arches, just caudal to the future site of the medial tongue bud. This thickening soon forms a down-growth known as the thyroid diverticulum. As the embryo elongates and the tongue grows, the developing thyroid gland descends into the neck, passing ventral to the developing hyoid bone and the lateral cartilages. The developing thyroid gland is connected to the tongue by the thyroglossal duct. The opening of this duct in the tongue is called the foramen cecum. The thyroid diverticulum is first hollow, but soon becomes solid and divides. The right and left lobes are connected by an isthmus that lies anterior to the second and third tracheal rings. By 7 weeks the thyroid gland has usually reached its final site in the neck. By this time the thyroglossal duct has normally degenerated and disappeared. A pyramidal lobe is present in about 50% of persons, and may be attached to the hyoid bone by fibrous or muscular tissue. The pyramidal lobe represents a persistent portion of the inferior end of the thyroglossal duct. The small opening of the thyroglossal duct persists as a small blind pit, the foramen cecum of the tongue. The lateral anlage arises as a diverticulum from the fourth and From the Department of Vascular Surgery, Leiden University Medical Center. Competition of interest: none. Reprint requests: Dr Evert-Jan F. Hollander, Leiden University Medical Center, Department of Vascular Surgery, Albinusdreef 2, Leiden, Zuid 2300 RC, The Netherlands (e-mail: [email protected]). 0741-5214/2004/$30.00 ⫹ 0 Copyright © 2004 by The Society for Vascular Surgery. doi:10.1016/j.jvs.2003.07.018
260
fifth pharyngeal pouches and forms the parafollicular cells, which produce calcitonin.1 ECTOPIC OR ACCESSORY THYROID GLAND Rarely, the thyroid gland fails to descend, resulting in a lingual thyroid gland.2 Very rarely, incomplete descent results in the thyroid gland appearing high in the neck, at or just inferior to the hyoid bone. Accessory thyroid tissue may appear in the tongue or in the neck superior to the thyroid gland. It originates from remnants of the thyroglossal duct, and may be found anywhere from the tongue to the usual site of the thyroid gland (Fig 1). Various extremely rare sites of ectopic thyroid gland have been reported, including submandibular localization. It may then have the same presentation as any other neoplasm of the submandibular space.1 DEVELOPMENT OF CAROTID BODY The carotid body is derived from both mesoderm and elements of the third branchial arch and neural crest ectoderm, but not from endoderm, like the thyroid gland. It is a pinkish gray structure, 3 to 4 mm in diameter, located within the adventitial layer of the posteromedial aspect of the common carotid bifurcation. Tumors arising from this body are called paragangliomas, because they arise from paraganglioma cells. No relationship to development of the thyroid gland is known.3 CASE REPORT A 39-year-old woman with swelling over the right carotid bifurcation was referred to our department with a presumed carotid body tumor. The swelling had been present and asymptomatic for years, with no progression. The family history for carotid body tumor was negative. We found a firm mass, which could be moved laterally but not in the craniocaudal direction, suggestive of
JOURNAL OF VASCULAR SURGERY Volume 39, Number 1
Hollander, Visser, and van Baalen 261
Fig 2. MRI scan shows a mass (2.8 ⫻ 2.3 ⫻ 3.3 cm) between the internal and external carotid arteries.
Fig 1. Ectopic thyroid gland. 1, Lingual thyroid; 2, intralingual thyroid; 3, thyreoglossus duct cyst; 4, low neck ectopia; 5, thyroid gland, normal position; 6, intratracheal position; 7, mediastinal position.
a mass at the carotid bifurcation. The diameter was approximately 4 cm; there were no signs of cranial nerve dysfunction. Laboratory testing showed no abnormalities. A magnetic resonance image (MRI) showed a mass (2.8 ⫻ 2.3 ⫻ 3.3 cm) between the internal and external carotid arteries. The typical characteristics of a carotid body tumor (homogeneous and highly vascularized mass) were described in the report (Fig 2). Intraoperatively, the tumor did not show the characteristic macroscopic aspect of a carotid body tumor. The suspicion of ectopic thyroid tissue was raised, and the tumor was excised. Histologic analysis showed an encapsulated tumor (4.1 ⫻ 3.0 ⫻ 2.8 cm) consisting of nodular thyroid tissue without any signs of malignancy. Postoperative evaluation with ultrasonography showed a normal thyroid gland in the proper median position. Additional scanning also showed a normal thyroid gland, without any accessory localization. Thyroid function tests yielded normal results. Furthermore, the MRI assessment was revised, which had been misinterpreted. In retrospect, the mass was heterogenous, with no typical vascular pattern. Fig 3 shows a typical MRI of a carotid body tumor.
DISCUSSION Ectopic thyroid tissue is defined as thyroid tissue not located anterolaterally to the second to fourth tracheal cartilages. Since 1869, when Hickmann4 first reported lingual thyroid, several reports of ectopic thyroid tissue have been published. The lingual location is most common,
Fig 3. MRI shows a typical carotid body tumor.
accounting for 90% of reported cases.5,6 Other rare sites of ectopic thyroid gland include the mediastinum,7 esophagus,8 lung,9 heart,10 aorta,11 and abdomen.12-14 In 70% to 80% of cases the ectopic thyroid tissue is the only functional thyroid tissue.4,15,16 The literature contains only 14 reports of ectopic thyroid tissue located in the submandibular region.17-30 The simultaneous finding of submandibular ectopic thyroid tissue and a functional thyroid gland in its proper location is extremely rare. Sambola-Cabrer et al24
JOURNAL OF VASCULAR SURGERY January 2004
262 Hollander, Visser, and van Baalen
first reported ectopic thyroid tissue in the submandibular location in combination with a normally located but atrophic thyroid gland. A submandibular ectopic thyroid gland with a normally functioning thyroid gland in its proper location has been reported only once.19 In 1988 Rubenfield et al28 reported ectopic thyroid tissue at the carotid bifurcation. In contrast to our case, they did not find a proper functioning thyroid gland in its normal location. Several theories have been postulated to explain the origin of the lateral thyroid gland. Displacement during the course of embryonal development seems a logical explanation. The most accepted hypothesis for ectopic submandibular thyroid tissue in the absence of a normally located thyroid gland might represent dysembryoplasia of the lateral anlage, with nonmigration and agenesis of the median anlage. Nicastri et al31 reported that benign thyroid tissue may also metastasize to the cervical lymph nodes. From the point of view of a vascular surgeon, different causes of neck masses can be confused with carotid body tumors. These include metastatic cancer to the cervical nodes, branchial cleft cyst, and low parotid tumor. It is clear that an accurate preoperative diagnosis of a tumor mass in the neck region is important in clinical management. According to our findings, the possibility of ectopic thyroid tissue, although extremely rare, should also be considered if MRI findings are not completely typical. Standard management, that is, excision biopsy of the neck mass, can lead to irreversible hypothyroid disease, because in most cases it is the only functional thyroid tissue in the body. Careful additional analysis, including the thyroid gland, should therefore be considered preoperatively. In all cases diagnostic excision of the lesion should be performed; however, thyroid function tests can be important for adequate postoperative follow-up of thyroid function. REFERENCES 1. Moore KL. The developing human: clinically oriented embryology. 4th ed. Toronto: W.B. Saunders; 1988. p 184-7. 2. Hazard JB, Smith DE. The thyroid. Baltimore, Md: Williams & Wilkins; 1964. p 26. 3. Dean HD. Carotid body tumors. In: Sabiston DC Jr, editor. Sabiston’s textbook of surgery. 15th ed. Philadelphia: W.B. Saunders; 1997. p 1660. 4. Hickmann W. Congenital tumor of the base of the tongue, pressing down the epiglottis on the larynx and causing death by suffocation sixteen hours after birth. Trans Pathol Soc Lond 1869;20:160-1. 5. Larochelle D, Arcand P, Belzile M, et al. Ectopic thyroid tissue: a review of the literature. J Otolaryngol 1979;8:523-30. 6. Pintar JE, Dominique CTA. Normal development of the hypothalamicpituitary-thyroid axis. In: Braverman LE, Utiger RD, editors. Werner
7. 8. 9. 10. 11. 12.
13. 14. 15. 16. 17. 18.
19. 20. 21.
22. 23. 24. 25.
26. 27. 28.
29.
30. 31.
and Jugbar’s the thyroid. 6th ed. Philadelphia, Pa: Lippingcott; 1991. p 11-4. Arriaga MA, Meyers EN. Ectopic thyroid tissue in the retroesophageal superior mediastinum. Otolaryngol Head Neck Surg 1988;99:338. Whale HL. Esophageal tumor of thyroid tissue. BMJ 1987;2:1921. Simon M, Baczako K. Thyroid inclusion in the lung: metastasis of an occult carcinoma or ectopia? Pathol Res Pract 1989;184:263. Casanova JB, Daly RC, Edwards BS, et al. Intracardiac ectopic thyroid. Ann Thorac Surg 2000;70:1694-6. Williams RJ, Lindop G, Butler J. Ectopic thyroid tissue on the ascending aorta: an operative finding. Ann Thorac Surg 2002;73:1642-3. Gungor B, Kebat T, Ozaslan C, et al. Intraabdominal ectopic thyroid presenting with hyperthyroidism: report of a case. Surg Today 2002; 32:148-50. Shiraishi T, Imai H, Fukutone K, et al. Ectopic thyroid in the adrenal gland. Hum Pathol 1999;30:105-8. Jamshidi M, Kasirye O, Smith DJ. Ectopic thyroid nodular goiter presenting as a porta hepatis mass. Am Surg 1998;64:305-6. Meyerson M, Smith HW. Lingual thyroid: a review. Conn Med 1966; 30:341-4. Noyek AM, Friedberg J. Thyroglossal duct and ectopic thyroid disorders. Otolaryngol Clin North Am 1981;14:187-201. Kumar R, Sharma S, Marwah A, et al. Ectopic goiter masquerading as submandibular gland swelling. Clin Nucl Med 2001;26:306-9. Feller KU, Mavros A, Gaertner HJ. Ectopic submandibular thyroid tissue with a coexisting active and normally located thyroid gland: case report and review of the literature. Oral Surg 2000;90:618-23. Akoz T, Erdogan B, Ayham M, Cinar F. Ectopic submandibular thyroid tissue. Rev Laryngol Otol Rhinol (Bord) 1998;119:323-5. Temmel AF, Baumgartner WD, Steiner E, et al. Ectopic thyroid gland simulating a submandibular tumor. Am J Otolaryngol 1998;19:342-4. Di Benedetto V. Ectopic thyroid gland in the submandibular region simulating a thyroglossal duct cyst: a case report. J Pedriatr Surg 1997;32:1745-6. Sironi M, Assi A, Andruccioli M, Spreafico G. Submandibular ectopic thyroid gland. Clin Nucl Med 1996;21:585. Hansen LT, Christensen PH. Ectopic thyroid gland in the submandibular region. Ugeskr Laeger 1996;158:3324-5. Sambola-Cabrer I, Fernandez-Real JM, Ricart W, et al. Ectopic thyroid tissue presenting as a submandibular mass. Head Neck 1996;18:87-90. Morgan NJ, Emberton P, Barton RP. The importance of thyroid scanning in neck lumps: a case report of ectopic tissue in the right submandibular region. J Laryngol Otol 1995;109:674-6. Latimer J, Lindsay KA. Case report: lingual thyroid in association with lateral ectopic thyroid mass. Clin Radiol 1995;50:501-2. Aguirre A, de la Piedra M, Ruiz R, Portilla J. Ectopic thyroid tissue in the submandibular region. Oral Surg 1991;71:73-6. Rubenfeld S, Joseph UA, Schwartz MR, et al. Ectopic thyroid in the right carotid triangle. Arch Otolaryngol Head Neck Surg 1988;114: 913-5. Alsop JE, Yerbury PJ, O’Donnell PJ, Heyderman E. Signet-ring cell microfollicular adenoma arising in a nodular ectopic thyroid: a case report. J Oral Pathol 1986;15:518-9. Helidonis E, Dokaianakis G, Papazoglou G, et al. Ectopic thyroid gland in the submandibular region. J Laryngol Otol 1980;94:219-24. Nicastri AD, Foote FW Jr, Frazell EL. Benign thyroid inclusions in cervical lymph nodes. JAMA 1965;194:1.
Submitted May 21, 2003; accepted Jul 1, 2003.