The diagnostic accuracy of neck ultrasound, 4D-Computed tomographyand sestamibi imaging in parathyroid carcinoma.

Introduction: Our aim was to investigate the accuracy of available imaging modalities for parathyroid carcinoma (PC) in our institution and to identify which imaging modality, or combination thereof, is optimal in preoperative determination of precise tumor location.

Methods: All operated PC patients in our institution between 2000 and 2015 that had at least one of the following in-house preoperative scans: neck ultrasonography (US), neck 4D-Computed Tomography (4DCT) and 99mTc Sestamibi SPECT/CT (MIBI). Sensitivity, specificity and accuracy of PC tumor localization were assessed individually and in combination.

Results: 20 patients fulfilled the inclusion criteria and were analysed. There were 18 US, 18 CT and 9 MIBI scans. The sensitivity and accuracy for tumor localisation of US was 80% (CI 56-94%) and 73% respectively, of 4DCT was 79% (CI 58-93%) and 82%, and of MIBI was 81% (CI 54-96%) and 78%. The sensitivity and accuracy of the combination of CT and MIBI was 94% (CI 73-100%) and 95% and for the combination of US, CT and MIBI was 100% (CI 72-100%) and 100% respectively. The wash-out of the PC lesions, expressed as a percentage change in Hounsfield Units from the arterial phase to early delayed phase was -9.29% and to the late delayed phase was -16.88% (n=11).

Conclusions: The sensitivity of solitary preoperative imaging of PC patients, whether by US, CT or MIBI, is approximately 80%. Combinations of CT with MIBI and US increase the sensitivity to 95% or better. Combined preoperative imaging of patients with clinical possibility of PC is therefore recommended.