Ectopic Lingual Thyroid Masquerading as Thyroid Cancer Metastases

Shehzad Basaria, William H. Westra and David S. Cooper

Department of Medicine, Division of Endocrinology (S.B., D.S.C.), and Department of Pathology (W.H.W.), The Johns Hopkins University School of Medicine, and Sinai Hospital of Baltimore (D.S.C.), Baltimore, Maryland 21215

Address correspondence and requests for reprints to: David S. Cooper, M.D., Director, Division of Endocrinology, Sinai Hospital of Baltimore, 2401 West Belvedere Avenue, Hoffberger Building, Suite 56, Baltimore, Maryland 21215. E-mail: dcooper{at}lifebridgehealth.org


    Introduction
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 Introduction
 Case presentation
 Discussion
 References
 
The endocrine literature is replete with reports of false positive iodine-131 (131I) uptake in many parts of the body in patients with a history of thyroid cancer, thus simulating metastatic disease. The occurrence of lingual thyroid in patients with thyroid cancer is also a rarity. We present a case of an elderly woman with papillary thyroid cancer who had a positive 131I uptake at the level of the chin that was presumed to be metastatic disease. However, the histopathological diagnosis showed normal lingual thyroid tissue.


    Case presentation
 Top
 Introduction
 Case presentation
 Discussion
 References
 
A 72-yr-old woman presented in 1996 for further evaluation of enlargement of the right lobe of her thyroid that had been present since 1990. Approximately 30 yr before presentation, the patient had undergone left thyroid lobectomy for a benign nodule. In 1990, the patient developed enlargement of the right lobe. She was started on T4 suppression therapy, but over the next 6 years, an increase in size of the right lobe was noted. There was no history of radiation exposure to the neck, and the rest of her past medical history and family history was unremarkable. On examination in 1996, the right lobe was 7 x 4 cm in diameter. The left lobe was absent. Fine-needle aspiration biopsy of the right lobe revealed changes suggestive of papillary thyroid cancer. A noncontrast computed tomography (CT) scan confirmed the presence of the mass. One of the sections of the CT scan revealed a hypodense area at the base of the tongue that was considered to be an artifact. In July 1996, the patient underwent a right lobectomy. Pathologic examination revealed the presence of a 4.5-cm papillary thyroid cancer, without nodal involvement or extrathyroidal extension. After withdrawal from T4, a diagnostic radioiodine scan showed two distinct areas of uptake in the neck (Fig. 1AGo). Along with uptake in the thyroid bed (0.22%), there was also an area of greater uptake at the level of the chin (1.38%). Following the scan, in November 1996, the patient underwent ablation therapy with 105 mCi 131I. At that time, her serum TSH was 38.9 mU/L and thyroglobulin (Tg) was 72.1 ng/mL. A post-therapy scan again showed two distinct regions of uptake in the neck (Fig. 1Go, B and C), with no evidence of distant metastases. The patient was started on levothyroxine suppression therapy.



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Figure 1. A, The first diagnostic scan illustrating two distinct regions of 131I uptake: the thyroid bed and at the level of the chin. B, The post-therapy scan confirming the two distinct regions of 131I uptake. C, Magnified view of the head and neck area.

 
On withdrawal from T4 in June 1997, her serum TSH was 48.5 mU/L and Tg was 34.6 ng/mL. A second diagnostic scan was performed, which now demonstrated absent uptake in the thyroid bed, but significant residual uptake at the level of the chin, thought to be consistent with a metastasis at the base of the tongue (Fig. 2AGo). The patient was treated with 111 mCi 131I, and a post-therapy scan again failed to show any distant metastatic disease (Fig. 2BGo). In January 1998, following T4 withdrawal, her TSH was 78.4 mU/L and Tg was 17.5 ng/mL. A third diagnostic scan still showed an abnormal area of radioiodine accumulation at the level of the chin, with a 72-h uptake of 0.14%. The patient was not treated.



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Figure 2. A, The second diagnostic scan showing no uptake in the thyroid bed but significant uptake at the level of the chin. B, The post-therapy scan confirming the uptake at the level of the chin. No distant metastatic foci were seen.

 
In May 1999, scanning with recombinant human TSH (rhTSH) was performed. After two injections of rhTSH, her serum TSH increased to 31 mU/L and Tg to 10.4 ng/mL. A diagnostic scan again showed uptake at the level of the chin, which was 0.02% at 72 h. In July 1999, during withdrawal from thyroid hormone, her TSH was 75 mU/L and Tg 17.7 ng/mL. She was treated for a third time with 147.5 mCi 131I. A post-therapy scan again showed the abnormal area. A contrast enhanced CT scan of the neck, performed to further evaluate this abnormal uptake, showed a 1 x 1.2-cm enhancing mass at the base of the tongue (Fig. 3Go). The patient was then referred for an otolaryngologic evaluation. The lesion was not visualized by indirect laryngoscopy, but laryngoscopy under general anesthesia revealed a 2 x 2-cm well circumscribed firm white mass at the base of the tongue. An incisional biopsy specimen had a cut surface that was tan and smooth. There was no adherent skeletal muscle. Histologic examination showed numerous follicular structures embedded in a pink hyalinized stroma (Fig. 4AGo). The follicles were filled with pink colloid-like material and lined by uniformly spaced cuboidal epithelial cells. These cells had round uniform nuclei that lacked enlargement, grooves, optical clearing, or inclusions. An immunohistochemical stain for Tg (prediluted; Immunotech, San Jose, CA) demonstrated strong and diffuse staining of the epithelial cells and the intrafollicular colloid material (Fig. 4BGo). On T4 suppression, her serum TSH was 0.05 mU/L, free T4 was 1.8 ng/dL, T3 was 1.07 ng/mL, and Tg was less than 1.0 ng/mL.



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Figure 3. A contrast enhanced CT scan of the neck showing a 1 x 1.2-cm enhancing mass at the base of the tongue.

 


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Figure 4. Lingual thyroid tissue. a, The thyroid follicles are filled with colloid material and lined by a cuboidal epithelium without atypia (hematoxylin and eosin, x200). b, Immunohistochemical stain for Tg shows strong staining of the follicular epithelium and the intrafollicular colloid (Tg immunostain, x200).

 
In May 2000, scanning with rhTSH was performed. After two injections of rhTSH, her serum TSH increased to 174 mU/L and Tg to 6.2 ng/mL. The scan again showed uptake at the level of the chin, consistent with the uptake in the lingual thyroid.


    Discussion
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 Introduction
 Case presentation
 Discussion
 References
 
In this case report, we describe a patient with papillary thyroid cancer who had a lingual thyroid masquerading as a metastatic focus. Although the endocrine literature is replete with false positive 131I uptake simulating metastatic disease, only one published report has described lingual thyroid as the cause of false positive scan (1). However, in that patient, a biopsy was not performed and, therefore, histological evidence is lacking. To the best of our knowledge, the present case is the first histologically proven lingual thyroid simulating a metastatic focus in a patient with thyroid cancer.

False positive diagnostic 131I scans are due to uptake in many parts of the body and can be divided into physiologic and pathologic tracer uptake (2, 3). Physiologic uptake is usually seen in salivary glands, nasal mucosa, salivary secretions (tracheostomy site), lactating breast, liver, gastric mucosa, small and large intestine, urinary bladder, and in patients with hyperhiderosis (due to secretion of the tracer in sweat). Causes of pathologic uptake in the head and neck region are few. Meningiomas, dacrocystitis, prosthetic eye, sinusitis, dental disease (dental caries, periodontitis, pulpitis, periapical granuloma, etc.), sialadenitis, Warthin’s tumor, and hypertrophied thyroglossal duct remnant have all been reported as masquerading thyroid cancer metastasis.

Lingual thyroid is the most common location for ectopic thyroid tissue, accounting for 90% of the cases. Lingual thyroid is defined as the presence of thyroid tissue in the midline at the base of the tongue anywhere between the circumvallate papillae and the epiglottis. The prevalence of lingual thyroid is 1 in 100,000, and it is more common in women, with a female to male ratio ranging between 3:1 to 7:1. Embryologically, the thyroid originates at the foramen cecum, which is located at the junction of the anterior two thirds with the posterior one third of the tongue. Between the third to seventh week of gestation, the gland descends to form the normal thyroid gland in the pretracheal position (4). A failure to migrate normally may leave part or all of the thyroid tissue at the base of the tongue, or at any other position along the thyroglossal tract. The reported age at diagnosis of lingual thyroid has ranged from birth to 83 yr of age, with the mean of 40.5 yr. In 70–75% of patients with lingual thyroid, there is no eutopic thyroid tissue present in the pretracheal position (5).

Differentiation between lingual thyroid tissue and metastatic thyroid cancer may be difficult. On inspection, the surface of the lingual thyroid may be smooth or irregular. Occasionally, large blood vessels are present on the surface of lingual thyroid tissue, predisposing to ulceration and hemorrhage (6). Most detailed histological studies have shown that lingual thyroid tissue characteristically has an incomplete or poorly defined capsule. Therefore, benign lingual thyroid tissue may appear malignant due to what appears to be the invasion into the muscle, but this only signifies a defect in the capsule, resulting in intermingling of the glandular and the muscular elements (7). In addition, a variable amount of inflammatory infiltrate is not uncommon in lingual thyroid glands (8). The use of Tg immunoperoxidase staining may help in the diagnosis and characterization of the lingual mass, especially in patients who have received radioactive iodine therapy (as in our case), which distorts the histological architecture of the tissue. The use of Tg staining can also help in determining the etiology of a lingual mass of uncertain origin.

Interestingly, a kinetic analysis of iodine turnover in lingual thyroid tissue showed a biological half-life of 1.3 days compared with 100 days in the normal thyroid tissue (9). This phenomenon may explain why the lingual thyroid in the present patient was so resistant to ablation, compared with the remnant tissue in the thyroid bed. Even after almost 360 mCi radioiodine, the tissue was still present on a whole body scan after T4 withdrawal.

Although the present patient clearly had a benign process, cases of thyroid cancer metastasizing to the oral cavity have been reported. In one patient, metastatic foci of follicular thyroid cancer were present on the lower lip and on the dorsum of the tongue (10). To the best of our knowledge, this is the only case of thyroid cancer metastasizing to the tongue in the literature. In another patient, a calcified papillary thyroid cancer was found in the parapharyngeal space masquerading as a parotid mass (11). Hence, it is clear that metastases to the base of the tongue are a rare event. Therefore, if 131I uptake is seen in this area, lingual thyroid is the most likely explanation, even in a patient with known thyroid cancer. However, if the mass is painful or results in bleeding, a biopsy should be the next step because papillary carcinoma in an ectopic lingual thyroid tissue has been reported (12).

In summary, we describe a patient with papillary thyroid cancer and concurrent lingual thyroid tissue. When the two areas of distinct 131I uptake were seen in our patient, one in the thyroid bed and the other at the level of the chin, it was assumed that the latter corresponded to metastatic thyroid cancer at the base of the tongue. The patient was treated three times with radioactive iodine therapy for this lesion. Finally, on biopsy and Tg staining it was confirmed that this tissue is a normal ectopic lingual thyroid, without any evidence of malignancy. The reduction in the size of lingual thyroid following radioactive iodine therapy required much higher doses of radioiodine than were required to ablate the thyroid bed tissue.

In conclusion, lingual thyroid tissue can masquerade as a metastasis to the hypopharynx. The possibility of a lingual thyroid being present should be considered in all patients with a midline area of radioiodine uptake at the level of the chin, especially if it is relatively resistant to radioiodine ablation.

Received July 12, 2000.

Revised October 4, 2000.

Accepted October 4, 2000.


    References
 Top
 Introduction
 Case presentation
 Discussion
 References
 

  1. Sud AM, Gross MD. 1991 Radioiodine uptake following thyroidectomy for thyroid cancer. Recurrence or ectopic tissue? Clin Nucl Med. 16:894–897.[Medline]
  2. Sutter CW, Masilungan BG, Stadalnik RC. 1995 False-positive results of I-131 whole-body scans in patients with thyroid cancer. Semin Nucl Med. 25:279–282.[Medline]
  3. McDougall IR. 1995 Whole-body scintigraphy with radioiodine-131. A comprehensive list of false-positives with some examples. Clin Nucl Med. 20:869–875.[Medline]
  4. Arancibia P, Veliz J, Barria M, Pineda G. 1998 Lingual thyroid: report of three cases. Thyroid. 8:1055–1057.[Medline]
  5. Neinas FW, Gorman CA, Devine KD, Woolner LB. 1973 Lingual thyroid. Clinical characteristics of 15 cases. Ann Intern Med. 79:205–210.[Medline]
  6. Kansal P, Sakati N, Rifai A, Woodhouse N. 1987 Lingual thyroid. Diagnosis and treatment. Arch Intern Med. 147:2046–2048.[Abstract]
  7. Jones P. 1961 Autotransplantation in lingual ectopia of the thyroid gland: review of the literature and report of a successful case. Arch Dis Child. 36:164–170.[Medline]
  8. Ward GE, Cantrell JR, Allan WB. 1911 The surgical treatment of lingual thyroid. Ann Surg. 139:536–544.
  9. Ramos-Gabatin A, Pretorius HT. 1985 Radionuclide turnover studies on ectopic thyroid glands–case report and survey of the literature. J Nucl Med. 26:258–262.[Abstract]
  10. Whitaker B, Robinson K, Hewan-Lowe K, Budnick S. 1993 Thyroid metastasis to the oral soft tissues: case report of a diagnostic dilemma. J Oral Maxillofac Surg. 51:588–593.[Medline]
  11. Carter LC, Uthman A, Drinnan AJ, Loree TR. 1997 Diagnostic dilemma involving calcification in the parapharyngeal space: metastatic thyroid carcinoma masquerading as a deep lobe parotid mass. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 84:697–702.[Medline]
  12. Casella A, Pisano R, Navarro Cuellar C, Llopis P, Mallagray R, Lavorgna G. 1999 Papillary carcinoma of the base of the tongue. Case clinic. Minerva Stomatol. 48:535–538.[Medline]