Endocrine Abstracts

Papillary thyroid carcinoma is one of the important but rare differential diagnosis of midline neck masses in adults. Other causes include thyroglossal duct cyst (TGDC) which is the commonest, ectopic thyroid gland, lymph node enlargement, and dermoid cyst. We report a rare case of unusual presentation of papillary thyroid cancer in a TGDC.

Case report

A 40-years-old female patient presented with a midline mass in the upper part of the neck. It was neither associated with pain nor dysphagia, or dysphonia. The mass was hard, mobile, non-tender, measuring 1×2 cm. Thyroid function tests were normal. On bedside neck ultrasound, the mass was hypoechoic, heterogenous, hypovascular, measuring 0.7×1.2 cm with irregular margins and multiple microcalcifications. there were two small hypoechoic hypovascular nodules in the right thyroid lobe measuring 0.7×0.6 cm and 0.5×0.5 cm respectively. There was no significant cervical lymphadenopathy. Ultrasound guided FNA from the midline mass and from the thyroid nodules were both positive for papillary thyroid carcinoma (PTC). Thyroglobulin determination in the needle washout from the midline mass was significantly high. Patient underwent total thyroidectomy and level VI lymph node dissection in addition to surgical removal of the TGDC using Sistrunk’s procedure. Histopathological assessment confirmed the diagnosis of PTC in the right lobe of the thyroid and in the thyroglossal duct cyst. Five lymph nodes out of eight were PTC metastasis. The diagnosis of a multi-focal PTC in the thyroid gland (2 foci) with extrathyroidal extension to the TGDC and central lymph nodes was made. Following surgery, therapeutic strategy was completed with radioactive I¹³¹ ablation and suppressive levothyroxine therapy. Radioactive iodine total body scans have revealed no remnant thyroid tissue. Thyroglobulin levels were undetectable 12 months after follow-up.

Discussion

The development of carcinoma in TGDC is very rare but well recognized. It is diagnosed in approximately 0.7% to 1% of thyroglossal duct remnants. Clinical examination of TGDC almost always fails evaluate for potential of malignancy within the cyst. TGDC carcinoma should be suspected if neck U/S revealed any suspicious sonographic features and US-guided-FNA should be done as the next diagnostic approach. In our case, we have decided to complete by a radioactive iodine therapy because of the disease multifocality. In the absence of clear guidance and recommendations, the management of TGDC carcinoma depends on the clinical situation and the team experience.