Abstract
The sensitivity of local recurrence detection in differentiated thyroid cancer (DTC) is increased by measuring thyroglobulin in needle washouts from lymph node fine-needle aspiration biopsies (FNA-Tg). Recent studies have proposed minimum diagnostic threshold values for FNA-Tg and have reported interference from Tg antibodies (Tg Ab), leading to low or false-negative results. The aim of this study was to assess the utility of FNA-Tg in the diagnosis of local DTC recurrence in patients referred to a single pathology service used by our tertiary teaching hospital, the first such study in an Australian cohort. Data were collected from the pathology service database for FNA-Tg over an 18-month period, and the results of 69 FNA-Tg samples from 57 patients were obtained. FNA-Tg findings were compared with cytology and histology when patients proceeded to surgery. Using the functional sensitivity as the cut-off, detectable FNA-Tg (≥0.9 μg/l) had a sensitivity of 95.7%, specificity of 50% and positive predictive value of 95.7%. Our results suggest that detectable FNA-Tg leads to histological confirmation of local nodal DTC recurrence and would support a decision to proceed to surgery. Serum Tg Ab can, however, interfere with FNA-Tg measurements. Thus, we now recommend routine use of FNA-Tg washouts in all lymph node FNA biopsies for the detection of DTC recurrence.
Highlights
Differentiated thyroid carcinoma (DTC) is the most common endocrine malignancy, of which the majority are papillary thyroid carcinoma (PTC)
Fine-needle aspiration cytology (FNA-C) is used to differentiate benign from malignant lymphadenopathies; falsenegative (6–18%) (4, 5, 6) and non-diagnostic (6, 7, 8, 9) results are not uncommon, with cystic metastases and very small lymph nodes
It is accepted that the sensitivity of detecting DTC in lymph node FNA-C is increased by measuring thyroglobulin in needle washouts from FNA biopsy (FNA-Tg) (4, 5, 8, 10, 11, 12, 13, 14); the diagnostic threshold http://www.endocrineconnections.org
Summary
Differentiated thyroid carcinoma (DTC) is the most common endocrine malignancy, of which the majority are papillary thyroid carcinoma (PTC). Ultrasonography has high sensitivity in the detection of cervical metastases but low specificity due to frequently occurring benign lymphadenopathies (3). Fine-needle aspiration cytology (FNA-C) is used to differentiate benign from malignant lymphadenopathies; falsenegative (6–18%) (4, 5, 6) and non-diagnostic (up to 20%) (6, 7, 8, 9) results are not uncommon, with cystic metastases and very small lymph nodes.
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