Endocrine Abstracts

Introduction: Follow up of differentiated thyroid cancer requires periodic measurements of thyroglobulin (Tg) and Tg autoantibodies (TgAb) and neck ultrasound. Recurrence is suspected in presence of rising levels of Tg and/or TgAb. Positive cytology or detectable Tg in washout of fine needle aspiration (FNA) of neck lymph nodes or 131-I neck uptake confirm the diagnosis of metastatic lymph node.

Case report: We report on a 25 year-old Caucasian man, affected by a classic variant papillary thyroid carcinoma with lymph nodal involvement and lymphocytic thyroiditis who underwent total thyroidectomy plus central compartment lymph node dissection. Three months later he underwent residual thyroid tissue ablation by 131-I activity (30 mCi). A neck ultrasound performed 6 months later showed two lymph nodes suspicious for metastatic disease. In the following four years lymph nodes did not enlarge. Both cytological examination and measurement of Tg in washout turned out negative in two occasions. Tg remained undetectable while TgAb rose from a pre-surgical level of 16 IU/mL to 259 IU/mL. We treated the patient with a second 131-I activity (140 mCi). Whole body scan turned out negative. Because of this we decided to performe FNA of the suspicious lymph node which in the meanwhile was slightly enlarged (16 mm). Cytological examination was diagnostic for metastatic disease and Tg in washout fluid was 123 ng/mL. The patient subsequently underwent lymphoadenectomy. The histological examination confirmed the diagnosis of metastatic lymph node.

Conclusion: In this patient the rising of serum TgAb was the most sensitive marker predicting the recurrence of differentiated thyroid cancer. Indeed TgAb rise, in spite of constantly undetectable serum Tg and repeatedly negative FNA of neck lymph nodes, suggested the correct treatment.