Accurate preoperative localization of tumor-bearing lesions is crucial for the successful surgical management of suspected recurrent parathyroid carcinoma. The purpose of this study was to evaluate the diagnostic value of 99m-technetium-labeled methoxyisobutylisonitrile (99mTc-MIBI) single-photon emission computed tomography/computed tomography (SPECT/CT) and cervical ultrasound, individually and in combination, for preoperative localization of recurrent/metastatic lesions. We also analyzed the value of 99mTc-MIBI SPECT/CT in detecting ectopic lesions in patients with suspected recurrent parathyroid carcinoma.

Twenty-nine patients with suspected recurrent parathyroid carcinoma were included in this retrospective cohort study. Patients underwent preoperative 99mTc-MIBI SPECT/CT and cervical ultrasound. The reference standard was postsurgical histopathology. The sensitivity, specificity, positive predictive value (PPV), negative predictive value, and accuracy of the two diagnostic modalities alone and in combination were analyzed.

Of the 29 patients, histopathological results revealed 48 metastases/recurrent lesions in 26 patients. The diagnostic value of 99mTc-MIBI SPECT/CT, cervical ultrasound, and the two modalities in combination were compared for the 27 patients who underwent new cervical surgery. Patient-level analysis of the combined use of 99mTc-MIBI SPECT/CT and cervical ultrasound had the highest sensitivity (100.00%) and accuracy (96.30%). At the lesion level, 99mTc-MIBI SPECT/CT had the highest specificity and PPV, at 100.00% respectively, whereas the combined use of 99mTc-MIBI SPECT/CT and cervical ultrasound had the highest sensitivity, at 97.62%. Moreover, 99mTc-MIBI SPECT/CT detected six ectopic lesions, and five of them showed increased 99mTc-MIBI uptake.

The combined use of 99mTc-MIBI SPECT/CT and cervical ultrasound is the most efficient strategy in the diagnosis of parathyroid carcinoma relapse, whereas 99mTc-MIBI SPECT/CT is the preferred method for localizing and analyzing cervical and extra-cervical lesions before the new surgery.