Abstract: Objective: To investigate the value of ^99mTc-MIBI SPECT/CT parathyroid imaging and ultrasound in incidental detection of neck carcinoma. Methods: A total of 952 patients with clinically suspected primary hyperparathyroidism (PHPT) undertaken ultrasonography and ^99mTc-MIBI SPECT/CT of base of skull, neck and thorax were enrolled. Each case with suspected lesion was analyzed and correlated with pathological finding. The frequency of carcinoma on SPECT/CT performed for PHPT was calculated. Sensitivity, specificity and accuracy for head and neck carcinoma, especially thyroid carcinoma of both the SPECT/CT and ultrasound were calculated. Results: Among the 952 patients, a total of 304 patients were treated with surgery and 352 pathological results were obtained. And finally, 64 carcinoma (83 sites) were found. The anatomical distribution was as follows: 22 (34.38%) were parathyroid carcinoma, 24 (37.50%) were papillary thyroid carcinoma, 4 (6.25%) were follicular thyroid carcinoma, 7 (10.94%) were medullary thyroid carcinoma and 7 (10.94%) were other tumors. The sensitivity of SPECT/CT and ultrasound for neck carcinoma were 46.99% and 74.70%, respectively. Specificity was 91.21% for SPECT/CT and 94.79% for ultrasound. Accuracy was 81.79% for SPECT/CT and 90.51% for ultrasound. The sensitivity of SPECT/CT and ultrasound for thyroid carcinoma were 39.31% and 80.43%, respectively. Specificity was 90.12% for SPECT/CT and 92.73% for ultrasound. Accuracy was 84.10% for SPECT/CT and 91.28% for ultrasound. Conclusions: The concomitant occurrence of PHPT and neck carcinoma is not uncommon. Although ^99mTc-MIBI SPECT/CT plays an important role for the diagnosis and location of PHPT lesions, ultrasound is a better choice for detecting neck carcinoma, such as thyroid carcinoma accompanied the PHPT.

Key words: Primary hyperparathyroidism (PHPT), Neck carcinoma, Thyroid carcinoma, ^99mTc-MIBI SPECT/CT, Ultrasound