Unusual case of well-differentiated papillary thyroid carcinoma lacking thyroglobulin expression while still concentrating radioiodine.

We present an unusual case of a well-differentiated papillary thyroid carcinoma with bilateral lung metastases. Despite undetectable serum thyroglobulin (Tg) on thyroid stimulating hormone (TSH) stimulation and no immunohistochemical evidence of Tg expression in the primary tumour, the patient showed significant uptake of radioiodine in both lungs. After five cycles of high dose radioiodine therapy, the patient went into complete remission and therefore had an excellent response to radioiodine treatment. This case is a rare exception to the rule of Tg production as a prerequisite for differentiated thyroid cancers to concentrate radioiodine.