Increasing diagnostic effectiveness of thyroid nodule evaluation by implementation of cell block preparation in routine US-FNA analysis

Abstract

Objective: Ultrasound-guided fine-needle aspiration (US-FNA) biopsy has proven to be an accurate and efficient tool in thyroid nodule evaluation. We evaluated whether cell block adds to the diagnostic accuracy of US-FNA. Subjects and methods: Three hundred twenty-eight consecutive patients underwent US-FNA, cytology and cell block evaluation. Six slides were prepared for each patient and stained by Papanicolaou and Giemsa techniques. The residual hemorrhagic aspirate in the syringe and needle was fixed in 10% formalin and paraffin-embedded (cell block). The histological sections were examined as a complementary diagnostic tool to US-FNA. Results: The study population comprised 89% females and the mean age was 57.4 ± 13.7 years. The mean nodule size was 2.3 ± 1.2 cm. US-FNA cytological results were as follows: Bethesda I, 17.1% (n = 56); Bethesda II, 61.6% (n = 202); Bethesda III, 9.5% (n = 31); Bethesda IV, 5.8% (n = 19); Bethesda V, 2.4% (n = 8), and Bethesda VI, 3.6% (n = 12). Cell blocks were obtained in 100% of cases and were considered diagnostic in 89.6%. Combined cytological and cell block (cyto-cell block) results were as follows: unsatisfactory, 4.3% (n = 14); benign, 72.6% (n = 238); indeterminate, 11.3% (n = 37); follicular lesion, 5.8% (n = 19); suspicious for malignancy, 2.4% (n = 8), and malignant, 3.6% (n = 12). The sensitivity and specificity for cyto-cell block was 100% and 90%, respectively, and the accuracy was 94%. Cyto-cell block analysis reduced the rate of unsatisfactory samples (p < 0.001). Conclusions: The cyto-cell block interpretation improved the efficiency of US-FNA. This simple, fast and low-cost technique should be used as an adjunctive test in thyroid nodule evaluation.