Assessment of Nondiagnostic Ultrasound-Guided Fine Needle Aspirations of Thyroid Nodules

Thyroid nodules are common. Evaluation of patients with thyroid nodules typically includes fine needle aspiration biopsy (FNA), an approach that has proven to be accurate for the detection of thyroid cancer. Although the majority of biopsies are adequate for a cytological diagnosis, up to 20% will be insufficient or nondiagnostic. Current opinion suggests that such aspirates should be repeated, although no systematic study has investigated the usefulness of this approach, especially when ultrasound guidance is used to direct the initial FNA. We sought to define the predictors and optimal follow-up strategy for initial nondiagnostic ultrasound-guided FNAs of thyroid nodules. Data were collected for all patients at the Brigham and Women's Hospital Thyroid Nodule Clinic between 1995-2000 who underwent ultrasound-guided FNA of a thyroid nodule. All patients with nondiagnostic cytology were advised to return for a repeat ultrasound-guided FNA. Patient age, gender, nodule size, cystic content, solitary vs. multinodular thyroid, and nodule location were documented and evaluated as possible predictors of a nondiagnostic biopsy in a multivariable model. The rate of diagnostic cytology obtained on repeat ultrasound-guided FNA was calculated. A total of 1128 patients with 1458 nodules were biopsied over a 6-yr period. A total of 1269 aspirations (950 patients) were diagnostic, and 189 (178 patients) were nondiagnostic. The cystic content of each nodule was the only significant independent predictor of nondiagnostic cytology (P < 0.001). The fraction of specimens with initial nondiagnostic cytology increased with greater cystic content (P < 0.001 for trend). A diagnostic ultrasound-guided FNA was obtained on the first repeat biopsy in 63% of nodules and was inversely related to increasing cystic content of each nodule (P = 0.03). One hundred and nineteen patients with 127 nodules returned for follow-up as advised, and malignancy was documented in 5%. Despite ultrasound-guided FNA, there remains a significant risk of initial nondiagnostic cytology, largely predicted by the cystic content of each nodule. Repeat aspiration is often successful and should be the standard approach to such nodules, given their risk of malignancy.