The patient was a 70-year-old woman with back pain and gait disturbance. Destructive changes of Th 12 and L 1 were detected on x-ray of the vertebrae. Laminectomy and biopsy of the tumor tissue was performed. The histology of the specimen showed metastatic follicular carcinoma of the thyroid. However, no tumor was palpable in the anterior neck region. Echography revealed a small nodule in the left lobe of the thyroid. A preoperative diagnosis of the occult carcinoma with vertebral metastases was made, and total thyroidectomy with bilateral cervical lymph node dissection was done. In the resected specimen, a firm tumor measuring 1.0 × 1.0 × 0.6cm in size was found in the left lobe. Histologically, the firm nodule in the left lobe showed the sclerosing type of follicular carcinoma, and no metastases of the lymph nodes were found. After operation, radiation therapy using 131I (100mCi) was done.
In our department, we have had 757 cases of primary thyroid carcinoma. These include 10 cases of occult carcinoma, 9 cases (1.1%) found by lymph node metastases, and only one case (0.1%) detected by distant metastasis. It is considered that occult carcinoma of the thyroid found by distant metastasis is very rare.
