title: Thyroid gland metastasis arising from primary liver cholangiocarcinoma: The first case report involving surgical operation.
abstract: BACKGROUND
  A primary cancer causing thyroid metastasis is extremely rare. In western countries, the most common primary tumors causing thyroid metastases include kidney, lung, breast, and gastrointestinal cancers. In contrast, breast is the most common primary site, followed by kidney, colon, and lung cancers in Korea. To the best of our knowledge, surgically confirmed thyroid metastasis from cholangiocarcinoma has not been reported. Herein, we report the first case of thyroid metastasis secondary to cholangiocarcinoma on which surgery was performed.
  
  
  METHODS
  A 55-year-old man was diagnosed with hepatic malignancy in December 2008. He subsequently received 2 cycles of transarterial chemoembolization and 4 cycles of radio-frequency ablation between 2008 and 2010. At follow-up in January 2011, brain metastasis was identified in the right parietal area secondary to cholangiocarcinoma. In April 2011, the patient was found to have palpable masses on the left thyroid and lateral neck. The patient subsequently underwent total thyroidectomy followed by left radical neck dissection. Intraoperatively, an ill-defined mass measuring 6.0 cm was found infiltrating the subcutaneous tissue into the prevertebral fascia. Microscopic and immunohistochemical findings confirmed that the thyroid masses and lymph nodes were metastatic cholangiocarcinoma.
  
  
  CONCLUSIONS
  Positive immunohistochemical staining for cytokeratin 7, cytokeratin 19, and AFP and negative results for TG, TTF-1, and cytokeratin 20 can be definitely helpful in arriving at a correct diagnosis.
  
  
  CONCLUSIONS
  To the best of our knowledge, this is the first case report on surgically resected thyroid and lateral neck metastases secondary to cholangiocarcinoma.
authors.affiliation: Department of Surgery, Chonnam National University College of Medicine, Gwangju, Republic of Korea.
authors.forename: Min Ho
authors.initials: MH
authors.lastname: Park
authors.forename: Jin Seong
authors.initials: JS
authors.lastname: Cho
authors.forename: Ji Shin
authors.initials: JS
authors.lastname: Lee
authors.forename: Hee Kyung
authors.initials: HK
authors.lastname: Kim
authors.forename: Jung Han
authors.initials: JH
authors.lastname: Yoon