Solitary Pulmonary Metastasis of a Thyroid Papillary Microcarcinoma, Masquerading as Primary Lung Cancer

ABSTRACT

Although pulmonary metastasis of thyroid cancer is not uncommon, it mostly occurs as multiple discrete nodules on the lung parenchyma. Because thyroid cancer presenting with an isolated large lung mass is extremely rare and the diagnosis is frequently based on small pieces of tissue obtained by a fine needle, the wrong diagnosis such as lung cancer is prone to be made. A 60-year-old man was admitted for evaluation of a lung mass detected on chest radiography. Cytological examination of the bronchial washing specimens suggested adenocarcinoma. Surgery for early lung cancer was performed considering that no other abnormalities were found during the work-up that included 18-fludeoxyglucose positron emission tomography computer tomography (18FDG-PET/CT). Unexpectedly, the diagnosis of papillary thyroid cancer with lung metastasis was made, which prompted us to evaluate the thyroid gland and then remove the primary cancer by subsequent operation. Although it is uncommon, physician should be aware of this possibility, which could help to avoid the wrong diagnosis. Here we report on a typical case of solitary pulmonary metastasis of thyroid cancer and we summarize the previously reported cases with a review of the relevant literature.