Acute and Transient Thyroid Swelling Following Fine-Needle Aspiration Biopsy: Its Prevalence, Clinical Features, and Ultrasonographic Findings

ABSTRACT Objective: Acute diffuse swelling of the thyroid gland in the absence of hematoma formation is a rare complication following fine-needle aspiration biopsy (FNAB) that often resolves spontaneously. This complication has not been investigated in a large number of cases. Therefore, this study investigated the prevalence, clinical features, and ultrasonographic findings of acute and transient thyroid swelling after FNAB. Methods: We performed 16,817 FNABs for 9,596 thyroid nodules between 2011 and 2015. Results: We identified 10 patients (8 women and 2 men) with acute and transient thyroid swelling without significant hematoma. The biopsied nodules were multi-nodular goiter (likely adenomatous goiter; n = 7), solitary thyroid nodule (including one follicular adenoma; n = 2), and papillary carcinoma (n = 1). The thyroid glands enlarged by 1.3- to 4.7-fold, accompanied with anterior neck pain and/or swelling immediately after FNAB in five cases, 5 to 15 minutes after FNAB in two, and 1 to 2 hours after FNAB in three. Ultrasonography revealed dendritic hypoechoic lesions (hypoechoic “cracks”) scattered throughout the swollen thyroid gland in all cases. Hypoechoic “cracks” did not show blood flow signal by color-flow Doppler imaging. Seven cases were treated with glucocorticoids, and three cases with smaller goiters were observed with neck cooling. Swelling of the thyroid gland subsided within several hours after symptom onset. Conclusion: The prevalence of acute and transient thyroid swelling was 0.10% (10 of 9,596 nodules). Hypoechoic “cracks” throughout the diffusely swollen thyroid gland were the ultrasonographic feature of this FNAB complication, despite pathologic differences in the biopsied nodules and different time intervals between FNAB and onset of acute thyroid swelling. Abbreviation: FNAB fine-needle aspiration biopsy