A 78-year-old man was referred to our hospital because of a tumor shadow in the right lower lung field on a chest x-ray film at a medical checkup. Chest CT and PET/CT scans revealed a 3.2-cm tumor in the middle lobe of the right lung and abnormal uptakes of FDG in the lower part of the right lobe of thyroid, right supraclavicular lymph nodes, and subcarinal lymph nodes. A CT-guided biopsy of the lung tumor revealed squamous cell carcinoma. Carotid ultrasonography revealed sporadic hypoechoic areas with the maximum diameter of 7 mm in the lower part of the right thyroid lobe, but we could not determine the areas as thyroid tumors. A fine needle biopsy of the right supraclavicular lymph nodes offered the diagnosis of lymph node metastasis of papillary carcinoma of the thyroid. We thus diagnosed the case as cN2 lung cancer associated with thyroid cancer, and performed right middle lobectomy of lung (ND2a-1) and right thyroid lobectomy (D2a).
CN3 lung cancers are not be candidates for surgery in many cases, if thyroid cancer is absent. In treating patients with lung cancer who also have nodules in the neck, we have not to make diagnosis easily as cN3 lung cancer, but have to differentiate from lymph node metastasis of thyroid cancer, parathyroid cancer, neurogenic cancer, or malignant lymphoma in order to pursue the surgical indication.