Abstract

OBJECTIVE:

This study aimed to assess the diagnostic accuracy of a specific ultrasound classification system in evaluating thyroid nodules with inadequate cytology, defined as a cytologic result that shows insufficient cellularity and does not provide useful information. Ultrasound diagnoses were made in accordance with a specially devised ultrasound classification system.

SUBJECTS AND METHODS:

From January 2008 to December 2009, 1036 patients with 1289 thyroid nodules (largest diameter ≥ 5 mm) diagnosed by ultrasound and subsequent ultrasound-guided fine-needle aspiration (FNA) were enrolled in the study. Each thyroid nodule was prospectively classified on the basis of its ultrasound features by a single radiologist into one of five diagnostic categories: benign, probably benign, borderline, possibly malignant, or malignant. Solid nodules were classified using all five categories, whereas partially cystic thyroid nodules were classified using four (borderline was omitted). Repeated ultrasound-guided FNA was performed on all nodules for which the initial ultrasound-guided FNA revealed inadequate cytology.

RESULTS:

Of 96 nodules with inadequate cytology (96/1289, 7.4%), 22 were surgically removed, and the ultrasound diagnoses and cytopathology results of all 96 were compared. A borderline ultrasound diagnosis was assigned to 13 nodules. The sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for all nodules excluding all the borderline nodules (100%, 95.1%, 33.3%, 100%, and 95.2%, respectively) and with four borderline nodules reclassified as benign (100%, 95.3%, 33.3%, 100%, and 95.4%, respectively). The values obtained with these approaches were not significantly different (p > 0.05).

CONCLUSION:

The selective use of repeated ultrasound-guided FNA for nodules with initial inadequate cytology may be preferable to its unconditional use depending on the ultrasound diagnoses of thyroid nodules.