as the thyroid gland descends from the foramen cecum to its location at the point below the thyroid cartilage , it leaves behind an epithelial trace known as the thyroglossal tract . incomplete atrophy of the thyroglossal tract , or retained epithelial cyst , creates the basis for the origin of a thyroglossal duct cyst ( 1 ) . a thyroglossal duct cyst is the most common anomaly in the development of the thyroid gland ( 2 ) . seventy percent are diagnosed in childhood and 7% are diagnosed in adulthood ( 3 ) . a 22-year - old female patient was admitted with the complaint of swelling in his neck . there was no history of dysphagia , hoarseness , or fever . in the physical examination , there was a painless cystic mass about 3.0  1.5 cm in size at midcervical line which moves with gulping . ultrasonography of the neck showed a well - defined , systic mass ( 23  18  12 mm in size ) with a echogenous component ( 7  7 mm in size ) ( fig . the pathologic report showed duct with stratified squamous epithelium , mild infiltration of lymphocytes , fibrotic stroma and many true papillary structures that lined by cuboidal cells , indicating a malignant papillary carcinoma arising in a thyroglossal duct cyst ( fig . the final postoperative pathology reported papillary carcinoma without any metastasis to the thyroid and cervical lymph nodes . one hundred mci i-131 radioactive iodide and thyroid suppression therapy was given after the operation . malignancy should be suspected if the cyst is hard , fixed , irregular , or displays sudden expansion with palpable neck lymph nodes ( 5 ) . the diagnosis is , however , often made postoperatively on histologic examination of the resected specimen . in one study the age at presentation ranged from 6 to 81 years , with an average of 39 years . women are affected more often than men ( 6 ) . to confirm a diagnosis of thyroglossal duct cyst , the following criteria should be fulfilled : the cyst must be located in the median region of the neck ; the cyst wall must be composed of cuboidal epithelial cells ; and lymphatic tissues and normal thyroid follicles must be present in the cystic wall ( 7 ) . malignant tumors developing from the thyroglossal duct have two origins : thyrogenic carcinoma arising from thyroembrionic remnants in the duct or a cyst , and squamous cell carcinoma arising from metaplastic columnar cells that line the duct ( 1 ) . more than 200 cases of thyroglossal duct carcinomas have been reported in which papillary carcinoma accounts for 80% of cases , with the rest being squamous cell carcinoma ( 8) . in our case , the presence of carcinoma within a thyroglossal duct and normal thyroid tissue support the diagnosis of papillary carcinoma arising in a thyroglossal duct remnant rather than a metastasis from a primary carcinoma of the thyroid gland . on ultrasonography , a benign thyroglossal duct cyst can be anechoic , homogenously hypoechoic , homogenously hyperechoic , or heterogenous in appearance . calcification is the hallmark of papillary carcinoma in a thyroglossal duct cyst ( 9 ) . in our case , apart from the cystic lesion , ultrasonography showed an echogenous component without calcification . the common surgical procedure used for a thyroglossal duct cyst is sistrunk s procedure . in case of malignancy , additional steps should consist of thyroidectomy , radioactive iodine and thyroid suppression ( 1 ) . in our case , this patient had no nodules in the thyroid gland , no previous exposure to radiation , no lymph node metastasis and no extra capsular spread of the thyroglossal duct cyst carcinoma . she needs further life - long follow - up with physical examinations and imaging studies . ethical issues ( including plagiarism , informed consent , misconduct , data fabrication and/or falsification , double publication and/or submission , redundancy , etc ) have been completely observed by the authors .
abstractthyroglossal duct cysts are the most common form of congenital cysts on the neck . 
 the incidence of thyroid papillary carcinoma in thyroglossal duct cyst is less than 1% . in most cases 
 the diagnosis is made postoperatively . 
 we present a 22-year - old female with thyroid papillary carcinoma arising from thyroglossal duct cyst , identified in pathologic study after sistrunk operation . in our case 
 there was neither invasion to adjacent tissue nor lymph node involvement . 
 the patient then underwent total thyroidectomy and bilateral neck dissection . 
 the patient was treated with radioactive iodide and thyroid suppression therapy was given as adjuvant treatment . 
 the patient has been following for two years without any metastasis .