Thyroglossal Duct Cyst Carcinoma

Thyroglossal duct cyst (TDC) is the second most common neck mass in a child occurring in 7% of the population. It's a benign cystic bump in the middle of the neck near the hyoid bone that moves with tongue protrusion. The diagnosis can be corroborated with ultrasound. Excision of the cyst and duct along with the central portion of the hyoid bone is curative (Sistrunk's procedure). A papillary carcinoma (CA) can arise from a preexisting TDC from the thyroembryonic follicular thyroid remnant cells. The incidence of papillary carcinoma is 1% in surgically removed TDC. 90% of TDC carcinomas are papillary or follicular in origin, 5% are squamous cell and the rest is anaplastic, Hurthle cell or adenocarcinoma. Median age of diagnosis of TDC carcinoma is 40 years. TDC-CA occurs de novo arising from ectopic thyroid gland tissue. They are not a metastasis from an occult thyroid primary and any lesion found in the thyroid gland represents a multifocal independent primary cancer. Females are more commonly affected. Cervical node metastasis from papillary TDC carcinoma occurs in 10-25% of cases. After finding a papillary carcinoma in the specimen of the excised TDC in a child there exists controversy whether performing a total thyroidectomy or not. Most cases are found incidentally after examining the specimen histologically. Once the diagnosis is established an ultrasound of the neck and thyroid gland should be performed along with FNA biopsy of any suspicious nodule in the thyroid gland or lymph node. Genetic testing for BRAF, N-RAS, and H-RAS should be performed. Low risk patients should be managed with only Sistrunk procedure and include those with less than 45 years of age, small tumors (< 1 cm), classic histology, no extracapsular spread, no vascular invasion, negative margins, no nodal or distant metastasis and a normal thyroid gland and neck by imaging studies. Without these criteria they are categorized as high risk and managed with total thyroidectomy with or without lymph node dissection if they are found to be FNA-positive, and radioiodine ablation therapy. Long-term follow-up is mandatory after primary Sistrunk procedure without total thyroidectomy. Prognosis of TDC carcinoma is excellent with five ad 10-year overall survivals of 100% and 96% respectively.

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