Ectopic Lingual Thyroid Masquerading as Thyroid Cancer Metastases

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. 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 × 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. 1A). 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. 1, B and C), with no evidence of distant metastases. The patient was started on levothyroxine suppression therapy.