Abstract
Thyroglossal duct cyst (TGDC) carcinoma (TGDC-Ca) is a rare tumor with just over 200 cases having been reported (1). The diagnosis of TGDC-Ca in most cases is incidental after surgical resection. Because it is generally benign, surgery for TGDC is usually not urgent. Here, we present a patient with TGDC-Ca with aggressive behavior including cervical node metastases.
A 25-year-old man visited our clinic with a 5-year history of an enlarging mass in the anterior neck (see Supplementary Data; available online at
At age 25, during the 2 months before visiting our clinic, he identified two growing neck masses. One was around the original mass and the other at right lateral neck. Physical examination (PE) revealed a smooth 4-cm anterior neck mass attached to the hyoid bone with cystic and hard portions. Another 2.5-cm soft mass in his right level IV area was also palpated. The nasal, oral, pharyngeal, and laryngeal areas were normal. Computed tomography showed a 3.0×1.2 cm heterogeneously enhancing mass in the midline of the anterior neck with normal thyroid lobes. Another 2.5-cm round solid mass was noted at the right level IV area. US-guided fine-needle aspiration cytology of both masses revealed papillary thyroid carcinoma (PTC). Serum triiodothyronine, thyroxine, and thyrotropin was normal, but thyroglobulin (Tg) was increased to 99.94 ng/mL (normal=1.40–78.00). He underwent total thyroidectomy, central neck dissection, right lateral selective neck dissection (level IV), and Sistrunk's operation (see Supplementary Data). Histopathology revealed normal thyroid lobes and a 1.9×1.4 cm PTC within the TGDC without hyoid bone involvement. Three of eight lymph nodes contained PTC (two of five central lymph nodes and one of three level IV lymph nodes). Eight weeks after surgery with 1-month thyroid hormone withdrawal, he was treated with 30 mCi 131I after negative whole-body scan with 2 mCi 131I. Fifteen months afterward the serum Tg was <0.099 ng/mL and the PE was negative for recurrence.
A TGDC is an epithelial connection between the thyroid gland and the foramen cecum. The duct is normally obliterated during the 8th to 10th week of gestation. If it does not undergo complete involution the residual TGDC can be a site for the development of a TGDC-Ca. TGDCs occur in ∼7% of the population (2). Their frequency of malignant transformation, usually to a PTC, is about 1% (2). PTCs that arise from TGDCs have a much lower prevalence of cervical node metastases than those of the thyroid gland (2,3). We believe that the cervical node metastases in our patient arose from a TGDC-Ca since there was no PTC in the thyroid lobes.
Appropriate management of TGDC-Ca has been debated. There is universal agreement that the Sistrunk's operation is the minimum and often the definitive treatment. If there is clinical or imaging sign of a synchronous lesion in the thyroid, a total thyroidectomy is advocated. Initial node dissection for N0 neck had no significant impact on the outcome. However, when cervical lymph node metastases are present, the reasonable approach is to perform a Sistrunk's operation, a total thyroidectomy, and appropriate selective neck dissection, followed by postoperative radioactive iodine therapy (3).
Even though there is a low prevalence of malignant transformation of TGDC, elective surgery is usually recommended for all patients with uncomplicated TGDC (4). In our patient, if surgery had not been delayed, the surgical strategy and its outcome would probably have been different. A Sistrunk's operation might have been sufficient if this had been performed when he was 20 years old. Notably, the majority of malignant transformations of TGDCs have been in adults. Surgeons should be aware of malignant transformation of TGDC in their preoperative work up and surgical planning in adult patients with anterior midline neck masses.