[Thyroglobulin levels in needle lymph node cytology for the detection of papillary thyroid cancer recurrence]

During the detection of neck recurrence in patients with Papillary Thyroid Carcinoma (PTC), sometimes it is difficult to distinguish metastatic from inflammatory neck lymph nodes. The measurement of serum thyroglobulin (sTg) under thyroid hormone suppression therapy the presence of serum thyroglobulin antibodies (sAbTg), the diagnostic whole body scan and cytology can give false negative results. Measurement of thyroglobulin in the washout fluid from fine-needle aspiration biopsy (FNAB) of suspicious neck lymph nodes could improve the diagnostic accuracy.

To evaluate the usefulness of detecting Tg in lymph nodes (LTg) suspicious by ultrasonography (US) and compare it to cytology.

Between the years 2004 and 2007 we prospectively studied 30 patients with PTC and cervical US findings of suspicious recurrence. LTg was assayed in US guided FNAB used for cytology.

Sixteen out of 30 patients underwent surgery using as selective criteria an LTg higher than sTg or a positive cytology. Surgery confirmed the presence of metastasis in all 15 patients with positive LTg (8 with positive cytology) and in 1 patient with negative LTg and positive cytology (a case with undifferentiated thyroid cancer). The sensitivity was 93.7% for LTg and 56.2% for cytology. We identified by LTg 3 of 6 patients with undetectable sTg and positive sAbTg.

The presence of LTg showed a higher sensitivity than cytology for the detection of cervical lymph node metastasis. This method is useful even in the presence of sAbTg.