RESUMO
INTRODUCTION: The aim of this study was to identify the ultrasound features which are associated with malignancy in subcentimetre thyroid nodules. METHODS: This retrospective study included 454 thyroid nodules <10 mm in size in 413 patients from 2012 to 2016, which were subjected to fine needle aspiration cytology. Each nodule was classified according to the ultrasound patterns of the 2015 American Thyroid Association guidelines and the high suspicion ultrasound features (solid, hypo-echogenicity, irregular margins, microcalcifications, taller-than-wide, interrupted rim calcifications, and extrathyroidal extension) were identified for evaluation of their diagnostic performance. RESULTS: Of the American Thyroid Association high suspicion ultrasound features, univariate analysis showed that hypo-echogenicity (sensitivity 81.6% (95% CI 65.7-92.3%), specificity 50.0% (95% CI 43.4-56.6%)), irregular margins (sensitivity 34.2% (95% CI 19.6-51.4%), specificity 92.2% (95% CI 88.0-95.3%)), microcalcifications (sensitivity 23.7% (95% CI 11.4-40.2%), specificity 91.0% (95% CI 86.5-94.3%)), and taller-than-wide (sensitivity 23.7% (95% CI 11.4-40.2%), specificity 92.2% (95% CI 88.0-95.3%)) were significantly associated with a malignant diagnosis. Amongst the above features, subsequent multivariate analysis identified a combination of hypo-echogenicity and irregular margins as significantly associated with malignancy. Our malignancy rates based on American Thyroid Association ultrasound patterns from benign to high suspicion were 0.0, 8.3, 3.9, 15.7, and 40.4%, respectively. The American Thyroid Association high suspicion ultrasound pattern had a sensitivity of 50.0% (95% CI 33.4-66.7%) and specificity of 84.5% (95% CI 79.2-88.9%). CONCLUSION: The presence of both hypo-echogenicity and irregular margins was significantly associated with malignancy in subcentimetre thyroid nodules in our study. Hence, subcentimetre nodules which are hypoechoic with irregular margins may warrant further follow-up.
RESUMO
In light of the rising rate of incidentally detected subcentimetre thyroid nodules due to improved surveillance and diagnostic imaging, the decision of whether to perform fine needle aspiration cytology is increasingly pertinent. We aim to assess (1) the sampling adequacy of fine needle aspiration cytology, (2) malignancy rate, (3) thyroidectomy rate and (4) diagnostic accuracy of fine needle aspiration cytology. A total of 245 subcentimetre nodules in 220 patients underwent fine needle aspiration cytology between 2011 and 2014. Medical records were reviewed for cytology results, subsequent management and histopathological results in the event the patient underwent thyroidectomy. Sampling adequacy was calculated as the percentage of diagnostic results (Bethesda II-VI). Malignancy rate was defined as the percentage of Bethesda IV-VI diagnoses. Amongst patients with Bethesda IV-VI diagnoses who underwent thyroidectomy, their cytology reports were correlated with post-operative histopathological findings. The sampling adequacy of fine needle aspiration cytology was 77.1%. Malignancy rate (Bethesda IV-VI) was 9.7%. The respective malignancy rates in the < 5 mm nodule group and ≥ 5 mm nodule group were 6.67 and 10.0%. In total, 79.2% (19/24) of the malignant nodules underwent surgical excision. The rest declined surgery and/or were lost to follow-up. Amongst the malignant nodules which were surgically resected, 84.2% (16/19) had definitive malignant histology. Five of these demonstrated multifocal carcinoma and/or extrathyroidal extension of carcinoma on histology. Initial fine needle aspiration cytology and subsequent histopathological diagnoses matched in all cases except for three that had false-positive fine needle aspiration cytology results. Majority of our patients with suspicious cytology results subsequently underwent thyroidectomy, notwithstanding the relatively lower diagnostic accuracy of fine needle aspiration cytology in subcentimetre thyroid nodules.
