Mediastinal lymph node involvement as the initial manifestation of occult thyroid cancer in the surgical treatment of lung cancer: Report of a case

A 63-year-old man was referred to our institute for the treatment of squamo us cell carcinoma of the upper lobe of his right lung. A right upper lobect omy of the lung was performed with a mediastinal lymph node dissection. The postoperative pathological examination of the dissected specimens revealed one of the superior mediastinal lymph nodes to be morbid with micrometasta sis of occult thyroid cancer, while no node involvement was seen due to lun g cancer. A right lobectomy of the thyroid gland with a modified radical ne ck dissection was done 4 years later after the confirmation of the absence of any recurrent sign of lung cancer. In the resected specimen, papillary t hyroid microcarcinoma was observed with several intraglandular metastases a nd right regional lymph node involvement. Eight months later, a new primary lung cancer developed in the left lung, and a left upper lobectomy of the lung with a mediastinal lymph node dissection was performed. At that time, the absence of mediastinal lymph node metastasis from lung cancer or thyroi d cancer was confirmed. Mediastinal lymph node involvement as the initial m anifestation of occult thyroid cancer in surgical treatment for lung cancer is rare, but it is important to be aware of the possibility of incidentall y detecting occult thyroid cancer in surgical dissections in this area for lung cancer. The appropriate surgical treatment should be determined while carefully considering the prognosis of the lung cancer as well as that of a ny coexisting malignancy.