To assess the value of CT in identification and diagnosis of benign and malignant calcified thyroid nodules.

Retrospective analysis was performed on the CT data of 313 surgically and pathologically confirmed cases with 378 calcified nodules. Based on the size, morphology, and number, calcification was divided into microcalcification (d≤2 mm and axis displayed in only one cross-section) , coarse calcification (d>2 mm or displayed in two or more cross-sections) , annular calcification (arc or annular) , and multiple microcalcifications (solitary multiple microcalcification without a soft tissue lump) ; a distribution of microcalcification, coarse calcification, and annular calcification as well as a clearer enhanced periphery or internal calcification than nonenhanced data in benign and malignant thyroid nodules were observed.

The 378 nodules consisted of 259 benign nodules (68.5%) (all were nodular goiters) and 119 malignant nodules (31.5%) (including 111 papillary thyroid carcinomas, 4 follicular carcinomas, 3 medullary thyroid carcinomas and 1 lymphoma) . Microcalcification was more common in malignant nodules (MNs) than in benign nodules (BNs) , with a rate of 43.6% vs 12.4%, respectively (P≤0.05) , and its sensitivity, specificity, positive predicted value, and negative predicted value were 42.9%, 87.6%, 61.4% and 76.9%, respectively. Coarse calcification, annular calcification, and clearer enhanced periphery or internal calcification than nonenhanced data were more common in BNs than in MNs, with rates of 52.9% vs 20.2% (P≤0.05) , 66.0% vs 42.0% (P≤0.05) and 43.2% vs 19.3% (P≤0.05) , respectively, whose sensitivity, specificity, positive predicted value and negative predicted value were 66.0% vs 22.4% vs 43.2%, 58.0% vs 86.6% vs 80.7%, 77.4% vs 78.4% vs 83%, and 43.9% vs 33.9% vs 39.8%, respectively. Two multiple microcalcifications without a soft tissue lump were MNs (papillary thyroid carcinoma) .

Microcalcification and multiple calcifications are conducive to the diagnosis of MNs, whereas coarse calcification, annular calcification, and clearer enhanced periphery or internal calcification than nonenhanced data benefit the diagnosis of BNs, but the low specificity and high false positive rate suggest that the judgment of BNs or MNs should not depend on coarse calcification alone.