Cytological results of ultrasound-guided fine-needle aspiration cytology for thyroid nodules: emphasis on correlation with sonographic findings

Abstract

Purpose: To compare the cytological results of ultrasound-guided fine-needle aspiration (US-FNA) cytology of thyroid nodules to sonographic findings and determine whether US findings are helpful in the interpretation of cytological results.

Materials and methods: Among the thyroid nodules that underwent US-FNA cytology, we included the 819 nodules which had a conclusive diagnosis. Final diagnosis was based on pathology from surgery, repeated FNA cytology or follow-up of more than one year. Cytological results were divided into five groups: benign, indeterminate (follicular or Hurthle cell neoplasm), suspicious for malignancy, malignant, and inadequate. US findings were categorized as benign or suspicious. Cytological results and US categories were analyzed.

Results: Final diagnosis was concluded upon in 819 nodules based on pathology (n=311), repeated FNA cytology (n=204) and follow-up (n=304), of which 634 were benign and 185 were malignant. There were 560 benign nodules, 141 malignant nodules, 49 nodules with inadequate results, 21 with indeterminate results, and 48 that were suspicious for malignancy. The positive and negative predictive values of the US categories were 59.1% and 97.0%, and those of the cytological results were 93.7% and 98.9%. The US categories were significantly correlated with final diagnosis in the benign (p=0.014) and suspicious for malignancy (p<0.001) cytological result groups, but not in the inadequate and indeterminate cytological results groups. The false positive and negative rates of cytological results were 1.9% and 3.2%.

Conclusion: Sonographic findings can be useful when used alongside cytological results, especially in nodules with cytological results that are benign or suspicious for malignancy.

Fig. 1

Final diagnosis of the study population. FNA, fine-needle aspiration; Op, operation; NIC, no interval change. ^*from operation, ^**from repeated FNA cytology or NIC.

Fig. 2

A 50-year-old female with papillary thyroid carcinoma. (A) Ultrasonography shows well-circumscribed and isoechoic nodule (arrow) with a shape that is taller than it is wide and internal microcalcification in the thyroid gland; this nodule was considered suspicious. (B) Fine-needle aspiration cytology was interpreted as adenomatous hyperplasia based on the presence of flat sheets of follicular cells in the bloody background (Giemsa stain ×200 original magnification). Because of the discordant results between the sonographic findings and the cytological results, surgical excision was performed. (C) Thyroidectomy specimen shows a typical papillary carcinoma nucleus with a few grooves, clearing and pseudoinclusions, compatible with papillary thyroid carcinoma (hematoxylin and eosin (H&E) ×400 original magnification).

Fig. 3

A 61-year-old female with papillary thyroid carcinoma. (A) Ultrasonography shows an irregular and marked hypoechoic nodule with a shape that is taller than it is wide and internal mixed calcification in the right thyroid gland; this nodule was considered suspicious. (B) This fine-needle aspiration cytology was interpreted as suspicious for papillary thyroid carcinoma based on the presence of a rare cluster of follicular cells cytological overlapping and nuclear clearing and grooves (Papanicolaou stain ×200 original magnification). (C) This thyroidectomy specimen shows a few papillae with typical nuclear features of papillary carcinoma, such as nuclear pseudoinclusion, clearing and grooves, compatible with papillary carcinoma (H&E, ×400 original magnification).