To investigate the diagnostic value of computed tomography（CT）histogram analysis for thyroid malignant solitary coarse calcification nodules（MSCN）.

A total of 89 thyroid solitary coarse calcification nodules（coarse calcification ≥5 mm, no definite soft tissue around calcification）confirmed either by surgery or histopathological examination in 86 patients enrolled in this study from Jan. 2009 to Dec. 2015 were evaluated, including 33 MSCN from 32 patients and 56 benign solitary coarse calcification nodules （BSCN）from 56 patients. Overall, 27 cut-off values were calculated by N（4≤N≤30）times of 50 Hounsfield units （HU）in the range of 200 HU to 1500 HU, and each cut-off value and the differences in the corresponding area percentages in the CT histogram were recorded for MSCN and BSCN. The optimal cut-off value and the corresponding area percentage were established by receiver operating characteristic（ROC）curve analysis.

In the 24 groups with an ROC area under the curve（AUC）of more than 0.7, at a cut-off value of 1150 HU and at an area percentage of no less than 98.4%, the ROC AUC reached a maximum of 0.86, and the accuracy, sensitivity, and specificity were 70.8%, 93.9%, and 57.1%, respectively. At a cut-off value of 450 HU and at an area percentage of no less than 46.3%, the accuracy, sensitivity, and specificity were 76.4%, 48.5%, and 92.9%, respectively. At a cut-off value of 550 HU and at an area percentage of no less than 81.5%, the accuracy, sensitivity, and specificity were 75.3%, 33.3%, and 100%, respectively.

In comparison with the cut-off value of 1150 HU with an area percentage of no less than 98.4%, the sensitivities for the cut-off value of 450 HU with an area percentage of no less than 46.3% and for the cut-off value of 550 HU with an area percentage of no less than 81.5% were lower; however, the specificities increased significantly, providing an important basis for reducing the misdiagnosis of MSCN.