New insight into ectopic thyroid glands between the neck and maxillofacial region from a 42-case study

BACKGROUND Ectopic thyroid is a rare disease. In the present study at the 9th People's Hospital in Shanghai, China, 42 patients' ectopic thyroid glands between the neck and maxillofacial region were subjected to a retrospective and transverse study based on data from 1978 to 2012 to explore the natural characteristics of ectopic thyroid. METHODS The patients' clinical data were collected. In addition, scintigraphy (Tc-99 m, Iodine-131), CT scan, histology and pathology were performed. The protein expression of thyroid transcription factor-1 (TTF-1), thyroglobulin (TG), calcitonin (CT), Ki-67 and parathyroid hormone (PTH) were analyzed from paraffin wax-stored specimens of ectopic thyroid tissue compared with those of orthotopic thyroid tissue. RESULTS There were 42 total ectopic thyroid patients, approximately 1.24 patients per year on average at our hospital. These patients were aged from 6 to 85 years old, and there were 35 females (83.3 %), seven males (16.7 %). In total, 27 of the patients had lingual thyroid (64 %); seven, sublingual thyroid (17 %); five, dual areas occupied by ectopic thyroid (12 %) and three, other types (7 %). The following conditions were also presented: nodular goiter (13 %), adenoma (8.7 %) and Hashimoto's thyroiditis (4.3 %), no malignancy and no accompanying ectopic parathyroid. TTF-1 expression was significantly higher in ectopic samples than that in orthotopic samples (P = 0.007), but CT and Ki-67 levels displayed no difference. PTH was negative in ectopic tissue. CONCLUSION Ectopic thyroid is a rare disease and females were more prone to the disease. The most frequent location was lingual thyroid. Nodular goiter, adenoma and Hashimoto's thyroiditis was observed as orthotopic thyroid without accompanying ectopic parathyroid. TTF-1 was highly expressed in ectopic tissue, which may be related to abnormal embryogenesis leading to the thyroid gland being in an abnormal position. The expression of calcitonin (CT) and Ki-67 was not increased, and there were no malignant cells in any sample, which could indicate that it is not easy for ectopic thyroids to become malignant between the neck and maxillofacial region.