Objective: To evaluate the incidence of focal lesions in the thyroid in the area of recently normalized iodine supply as well as to compare the efficacy of fine-needle aspiration biopsy (FNAB) of small (infracentimetric) and large thyroid lesions in this area.
Methods: The outcomes of 13,646 ultrasound (US) examinations, 13,437 US-guided FNABs of the thyroid and 1694 results of post-operative histopathological examinations were analysed.
Results: Infracentimetric nodules (INs < or = 10 mm) were revealed by US examinations in 43.5% of patients; in the majority of the cases (82.2%) INs were multiple. The percentage of revealed carcinomas by aspiration of INs is similar to that observed when large nodules (LNs > 10 mm) are examined cytologically. However, the efficiency of preoperative diagnosis of INs is lower than LNs with respect to both US selection of lesions for FNAB and the percentage of false negative results of FNAB (29.8 vs 5.4%, P<0.001). In post-operative histopathological examination, extrathyroidal extension of thyroid cancers was observed in nearly 30% of microcarcinomas.
Conclusions: In endemic or post-endemic areas, the efficiency of FNAB is lower in the case of small lesions than larger ones. In spite of this, the percentage of cytologically revealed carcinomas among small lesions is not lower than larger ones. Thus, it is particularly indicated to follow up small thyroid lesions with repeated US examinations in such areas.