A Patient with Primary Squamous Cell Carcinoma of the Thyroid Intermingled with Follicular Thyroid Carcinoma that Remains Alive more than 8 Years after Diagnosis
A 56-year-old man presented with a hoarse voice and a rapidly progressive mass on the right side of his thyroid gland that had developed over the previous three months. He had no clinical symptoms related to thyroid dysfunction. There was no history of radiation exposure to the neck and no family history of thyroid cancer. Five years earlier, he had been diagnosed with a carcinoid tumor in the left lobe of the lung by percutaneous biopsy at another hospital; the patient has been asymptomatic throughout the prior five-year period.\nA physical examination revealed a hard, non-tender mass with a maximum transverse diameter of 3 cm on the right side of the thyroid gland. Palpable lymphadenopathy was absent in the cervical and supraclavicular area, and a laryngoscopic examination showed no abnormal findings from the oral cavity to the larynx. Laboratory examination showed a serum TSH level of 3.22 mU/L (reference range 0.30~5.00), T3 1.66 nmol/L (0.92~2.78), T4 78 nmol/L (58~140), anti-thyroglobulin antibody 1 U/mL (0~100), anti-microsomal antibody 1 U/mL (0~100), and thyroglobulin 170.1 ng/mL (0~25). There were no abnormal findings on the hematologic and biochemical laboratory tests. Neck computed tomography (CT) showed a low attenuated, calcified mass with a maximum diameter of 3 cm on the right side of the thyroid gland (). An ultrasonography-guided fine needle aspiration and cytology (FNAC) showed a small number of benign follicular cells without atypical cells. Chest X-ray and CT showed a 1 cm sized nodule in the upper lingular segment of the left lung; this nodule was previously diagnosed as a carcinoid, and was noted to have decreased in size. However, three small nodules were newly detected in the left lower lobe of the lung by comparison with prior films (). The new nodules noted in the left lower lobe of the lung were diagnosed as follicular neoplasm by FNAC.\nThe patient underwent a total thyroidectomy without neck lymph node dissection for the presumed diagnosis of follicular thyroid carcinoma with lung metastasis. However, the histopathologic evaluation revealed a well-differentiated squamous cell carcinoma 3 cm by 3 cm in size in conjunction with follicular carcinoma (). Intermingled and transitional zones of squamous cell carcinoma and follicular carcinoma were present. The tumor was confined to the thyroid gland with internal necrosis and dystrophic calcification. Immunohistochemical staining for cytokeratin 19 was strongly positive for squamous cell carcinoma and negative for follicular carcinoma (). Immunohistochemical staining for thyroglobulin and thyroid transcription factor-1 (TTF-1); was positive for follicular carcinoma and negative for squamous cell carcinoma ().\nTwo weeks after surgery, a 18F-FDG whole body positron emission tomography (PET) was performed and abnormal uptake was identified in a right submandibular lymph node, bilateral jugulodigastric lymph nodes, T7 spine, and lingular segment of the left upper lung; these findings favored the presence of a malignancy. Magnetic resonance imaging (MRI) also demonstrated a Bull's eye lesion with slight enhancement at the T7 vertebral body, suggesting metastasis (). Metastatic squamous cell carcinoma was excluded by laryngoscopy, esophagogastroscopy, abdominal ultrasonography, neck and chest CT, and whole body PET. The patient underwent 5000 rads of adjuvant radiotherapy to the neck postoperatively. Considering the poor prognosis for patients with primary squamous cell carcinoma of the thyroid, we did not pursue a further work-up or aggressive treatment. The patient was treated with TSH suppressive therapy with 200 µg of L-thyroxine only.\nThree years later, lower extremity paraplegia suddenly developed after the patient had a fall. The thoracic spine MRI demonstrated a metastatic lesion with a compression fracture and an epidural mass formation at the T7 spine, and other newly appeared metastatic lesions on T1, T4, T5, T6 and T8 (). These lesions were treated with external radiotherapy. The patient seemed to have almost completely recovered from paraplegia after radiotherapy. At that time, a chest X-ray showed that the pre-existing nodules noted in the left lower lobe of the lung had increased in size, and that multiple nodules were newly present in the right upper lobe of the lung. Serum thyroglobulin levels were increased to 423.2 ng/mL on T4 suppression therapy.\nSeven years later, colon cancer was detected. A preoperative chest CT showed multiple new nodules in the left lower lobe of the lung. Percutaneous biopsy directed to a new nodule in the left lower lobe of the lung was undertaken, and histopathologic findings revealed metastatic follicular carcinoma originating from the thyroid. High dose radioactive iodine therapy was administered after the patient underwent colectomy for colon cancer. At that time, the serum thyroglobulin level was 530.7 ng/mL and the anti-thyroglobulin antibody titer was 1 U/mL on the T4 suppression therapy. The patient now remains alive in satisfactory condition more than eight years after being diagnosed with primary squamous cell carcinoma of the thyroid. Recently, his serum thyroglobulin level had increased to 1164 ng/mL on T4 suppression therapy.