Abstract
Purpose
The goal of this study was to estimate the risk of malignant thyroid nodules being
interpreted as benign based on ultrasound findings and to clarify the pathological
features of these malignant nodules.
Materials and Methods
We retrospectively re-evaluated ultrasound and pathological findings for 162 malignant
thyroid nodules that were initially interpreted as benign based on ultrasound findings
at Kuma Hospital between April 2012 and June 2015.
Results
The incidences of malignancy among “benign” thyroid nodules were 0.5% overall and
6.2% among resected nodules. In addition, 82.7% of thyroid nodules that were originally
judged to have low or very low suspicion patterns were subsequently re-categorized
as having high or intermediate suspicion patterns. The incidences of irregular margins
(63.6%) and low echogenicity (36.4%) were higher than those of punctate microcalcification
(17.9%) and the taller-than-wide shape (20.4%). Among microcarcinomas, the incidences
were 65.7% for irregular margins and 51.4% for low echogenicity. Rim calcification
with small extrusive soft tissue components and extrathyroidal extensions were not
observed. After re-evaluation, 40.0% of papillary thyroid carcinomas remained benign
based on their variants, such as the encapsulated, follicular, macrofollicular, and
oxyphilic cell variants.
Conclusion
We conclude that more careful observation, especially for lesions with irregular margins
and low echogenicity, can help improve the diagnostic accuracy of thyroid ultrasonography.
Furthermore, greater care may decrease the incidence of malignancy among thyroid nodules
with low or very low suspicion patterns. Some variants of papillary thyroid carcinoma
can have benign ultrasound findings.
Key words
thyroid - sonography - risk of malignancy - interobserver variation
