Usefulness of thyroglobulin measurement in fine-needle aspiration biopsy specimens for diagnosing cervical lymph node metastasis in patients with papillary thyroid cancer

The diagnosis of lymph node metastasis in patients with papillary thyroid cancer is an important factor when deciding to perform neck dissection at the initial surgery, as well as for evaluating the lymph node swelling after surgery. Ultrasound (US)-guided fine-needle aspiration biopsy cytology (FNAB-C) is the most useful technique for diagnosing lymph node metastasis. Recently, however, measurement of thyroglobulin in the wash-out of the needle (FNAB-Tg) has been proposed for early detection of neck lymph node metastasis in patients with differentiated thyroid cancer. The purpose of this study was to evaluate the usefulness of FNAB-Tg in detecting lymph node metastasis prior to initial or reoperative thyroid surgery. US-guided FNAB-C was performed on 129 enlarged lymph nodes of Ill patients before surgery. All of them were later histologically confirmed to contain metastasis. Immediately after obtaining an FNAB-C specimen, the needle was rinsed with 0.5 ml of normal saline solution, and the wash-out was subjected to measurement of the Tg level (FNAB-Tg). If the FNAB-Tg level was higher than the serum Tg of the patient, we diagnosed the lymph node as positive (metastatic lymph node). FNAB-Tg sensitivity was 81.4%, and FNAB-C sensitivity was 78.0%. Altogether, 4 (36.4%) of 11 cases judged "benign" and 6 (37.5%) of 16 cases judged "inadequate" by FNAB-C were positive by the FNAB-Tg measurement. Thyroglobulin measurement in fine-needle aspiration biopsy wash-out is thus a useful technique for diagnosing lymph node metastasis of papillary thyroid cancer.