Background: Calcification can be detected in both benign and malignant nodules and is often neglected by clinical physicians. The purpose of this study was to investigate the association of thyroid nodule calcification detected on ultrasound with thyroid carcinoma.
Methods: One hundred seven cases of thyroid carcinoma and 215 cases of benign thyroid nodules were selected from the records of inpatients of our hospital who had high-resolution ultrasonography preoperatively and pathologic diagnosis postoperatively between 2001 and 2004. The case numbers and percentage of calcification, fine stippled psammomatous (FSP), and non-FSP calcification in benign nodules and thyroid carcinoma, sex, and age groups (<45 years and >or=45 years) were retrospectively reviewed. Statistical analysis was performed using chi-square test and odds ratio. Sensitivity and specificity of calcification and FSP calcification on ultrasonography were also calculated.
Results: The incidence of calcification, non-FSP calcification, and FSP calcification were significantly higher in thyroid carcinoma than in the benign group (p < .001, p = .03, and p < .001, respectively). However, FSP calcification was more significant than the non-FSP calcification (p = .001) for predicting thyroid cancer. The incidence of non-FSP calcification and FSP calcification did not differ significantly between the sexes (p = .50 and p = .83, respectively). The relative risk of malignancy incidence was significantly higher in those younger than 45 years old with FSP calcification (p < .001). The incidence of non-FSP calcification was significantly higher in the older group (p = .03). The sensitivity of calcification and FSP calcification for the detection of malignancy was 63.55% and 24.30%, respectively; the specificity was 69.77% and 96.77%, respectively.
Conclusions: The detection of calcification on ultrasonography should increase the clinical index of suspicion for thyroid carcinoma and alert the physician. FSP calcification is valuable and has a very high specificity for predicting thyroid carcinoma, particularly for those younger than 45 years old or with calcified regional lymph nodes. To increase the sensitivity for the diagnosis of thyroid carcinoma, tests such as fine-needle aspiration cytology should also be performed. The use of these modalities could result in earlier detection of thyroid carcinoma. The use of ultrasound to detect calcification and FSP calcification is as efficient as thyroid papillary macrocarcinoma in predicting microcarcinoma.