MED-16. Metastatic thyroid cancer with a histologically normal thyroid.

Thyroid carcinoma is the most common endocrine malignancy, and it is estimated that as many as 10% of population may have histologic evidence of this tumor at autopsy. We discuss a case of papillary thyroid carcinoma that was presented with cervical lymphadenopathy with the thyroid gland clinically, radiologically and histologically entirely normal. The patient is a 38-year-old man who was presented with cervical lymphadenopathy and had an excision biopsy, which showed a mixture of metastatic, well differentiated papillary thyroid carcinoma with diffuse sheets of poorly differentiated carcinoma. Immunohistochemistry showed a strong expression of thyroglobulin in the papillary component and weaker patchy expression in the poorly differentiated area. Thyroid transcription factor-1 (TTF-1) was expressed in both the components. Thyroid ultrasound was unremarkable for any structural abnormality of the thyroid. Total thyroidectomy was done and the thyroid gland was completely examined with no histologic abnormality. Two of nine lymph nodes removed showed metastatic papillary thyroid cancer. Whole body I123 scan was done with patient's thyroid stimulating hormone (TSH) elevated to 135 mIU/ml and no activity was noted. Three months after his surgery he developed recurrent cervical lymphadenopathy with similar histology. One month later a new lymph node appeared. This raised a question of ectopic thyroid tissue harboring an occult thyroid cancer, which was excluded after repeated negative iodine scans. This is unique because patient had multiple recurrences of cervical lymph node metastases with the same histology even after total thyroidectomy and radioactive iodine I131 therapy with no clinical, radiological or histological evidence of cancer in thyroid. The patient also presents a challenging diagnostic and therapeutic dilemma as he may have ectopic thyroid cancer at unknown site and this tumor does not concentrate I131. To our knowledge this is the first case of papillary thyroid carcinoma presenting in this manner.

Vipul Brahmbhatt, Richard Jordon, MD, Patrick Costello, MD, and Alan Peiris, MD. Department of Medicine, East Tennessee State University, Johnson City, TN.