Background: High-resolution real-time ultrasonography (US) can detect chara
cteristics of thyroid nodules, but the US differentiation between malignant
nodules and benign nodules is not well described.
Hypothesis: Ultrasonography is useful for predicting malignancy of thyroid
nodules.
Design: A retrospective study of 329 thyroid nodules (greater than or equal
to5 mm) in 309 patients comparing US characteristics and pathological resu
lts.
Setting: A center for the treatment of thyroid diseases where about 1400 th
yroid operations are performed per year.
Patients: Between January 1 and June 30, 1999, 309 patients were examined b
y US before thyroidectomy.
Main Outcome Measure: The US characteristics to predict malignancy for both
follicular and nonfollicular neoplasms by means of multiple logistic regre
ssion analysis.
Results: The sensitivity of preoperative US diagnosis was 86.5% for nonfoll
icular neoplasms and 18.2% for follicular neoplasms. The specificity was 92
.3% and 88.7%, respectively. According to multiple logistic regression anal
ysis, margin, shape, echo structure, echogenicity, and calcification were r
eliable indication of malignancy in nonfollicular neoplasms. According to a
receiver operating characteristic curve constructed from this multiple log
istic regression analysis, the best point not to overlook malignancy is the
point at which sensitivity is 94% and specificity is 87%. The probability
of malignancy at this point: is greater than 0.2. For follicular neoplasms,
ultrasonographic diagnosis was unreliable, even when multiple logistic reg
ression analysis was applied.
Conclusion: We can predict malignancy of nonfollicular neoplasms of the thy
roid by using multiple logistic regression analysis based on only 5 feature
s: margin, shape, echo structure, echogenicity, and calcification.