Purpose: To determine which nodular areas provide most adequate and accurate material for cytology during US-guided fine-needle aspiration biopsy (FNAB) of thyroid nodules.
Material and methods: In a prospective multicentre study, US-guided FNAB (0.8 mm) was performed in 342 thyroid nodules (338 patients, 285 women, 18-83 years, 285 palpable). Histology was obtained in 169 nodules, revealing 75 neoplasms (44.4%) including 18 cancers (10.7%). In 206 solid nodules, 2 passes (central and peripheral) were compared. In 82 complex nodules, 2 passes (solid area and cystic area) were compared.
Results: The inadequacy rate was 16.4% and the false-negative rates were 2.2% and 28.1% for the diagnosis of cancer and neoplasm, respectively. In solid nodules, material was more adequate with peripheral passes compared to central passes, but the difference was not significant. In complex nodules, the inadequacy rate was much higher for passes in cystic areas (80.5%) compared to passes in solid areas (46.3%).
Conclusion: Cystic areas due to degeneration seldom provided adequate material when aspirated. Aspiration should always be obtained from solid areas, at best using US-guidance. Adenomas and non-neoplastic nodules were difficult to distinguish.