a 64-year - old female was diagnosed with thyroid cancer in 2004 and was treated by thyroidectomy . during follow - up , blood free t4 levels were increased and an i-131 whole body scan was performed . 1 ) . additional chest computed tomography ( ct ) showed a 1.2-cm - long nodule at the left lower lobe , which matched the location in the i-131 scan results ( fig . 2 ) . a thoracoscopic approach was first attempted , but failed due to adhesion of left upper lobe . thus , a thoracotomy was performed . a 1-cm - long nodule surrounded by pulmonary tissue was observed next to the inferior pulmonary vein . a blood vessel branching off from the pulmonary vein and going through the nodule was also observed . the blood vessel was ligated , excised , and isolated from the inferior pulmonary vein . endogia ( covidien , mansfield , usa ) was then used for wedge resection of the nodule ( fig . it was identified as ectopic thyroid tissue , but it was not observed to be malignant ( fig . 5 ) . the patient 's chest tube was removed on day 5 after surgery , and the patient was discharged on day 10 without other complications . the thyroid migrates from endodermal protrusion of the first and second pharyngeal arch at 3 weeks to 7 weeks of gestation . a thyroglossal duct forms along the descending path of the thyroid and undergoes atrophy during the embryonic stage . during this development , abnormal migration of the thyroid causes it to be misplaced , which is known as ectopic thyroid . the prevalence of ectopic thyroid is 1 in every 100,000 to 300,000 in the general population and 1 in 4,000 to 8,000 in patients with thyroid disease . ectopic thyroid is mostly symptomless , but can have various symptoms based on the size and location . in particular , when located inside or around the trachea , the patient may experience aphagia , hoarseness , dyspnea , or a foreign body sensation as the size increases . however , most cases of ectopic intrapulmonary thyroid are symptomless , as in this case study . it is observed through radiation screening and ct scans and is reported to cause dry cough , dyspnea , hemoptysis aphagia , and superior vena cava syndrome . in addition , it is reported that orthotropic thyroid coexists in all cases of intrapulmonary thyroid . radiologic examinations for diagnosis include ct , magnetic resonance imaging , tc-99 m , i-131 , and i-123 . blind bronchoscope aspiration and real - time ultrasound aspiration have been used to obtain samples for histological diagnosis . a differential diagnosis of ectopic intrapulmonary thyroid includes thyroid cancer metastasis , thymoma , neuroma , and germ cell tumor . among ectopic thyroid cases , prior to ectopic intrapulmonary thyroid treatment , the patient 's age , presence of orthotropic thyroid , symptoms due to nodules and their severity , thyroid hormone level , and malignancy potential need to be considered to perform surgical or medical treatment . depending on the position of the tissue , sternotomy or thoracotomy can be performed for surgical treatment . also , thoracoscopic treatment can also be considered . in conclusion , ectopic thyroid occurs due to early developmental differentiation problems and can be positioned in different locations based on thyroid development . it is usually symptomless , but can cause symptoms depending on its location , size , and malignance . this case reports a patient with a history of thyroid cancer and abnormal thyroid function . surgery was performed in order to determine malignancy , and to diagnose and treat the ectopic thyroid .