Anatomical and functional localization of ectopic parathyroid adenomas: 6-year institutional experience

Localization of ectopic parathyroid adenoma is highly important to guide surgery, thus reducing morbidity and rate of recurrent hyperparathyroidism. The aim of this study was to establish the incidence of ectopic parathyroid adenoma and evaluate the role of multimodality imaging in diagnosis.

We reviewed 656 imaging studies of patients referred for investigations of primary hyperparathyroidism. All patients suspected of having an ectopic adenoma had technetium-99m (99mTc) sestamibi (MIBI) and ultrasound of the neck. In addition, patients had cross-sectional imaging, either computed tomography (CT) or magnetic resonance imaging (MRI), in cases of suspected ectopic adenoma. Some patients also underwent angiography. Results were correlated with postoperative findings and histopathology to calculate sensitivity, specificity, positive and negative predictive values. The incidence of ectopic adenoma was also determined.

In our series, the incidence of ectopic adenoma was 1.4%, which is lower than earlier published reports in the literature. Eleven patients showed ectopic uptake suspicious of a parathyroid adenoma on 99mTc MIBI. CT confirmed the diagnosis of ectopic adenoma in seven patients and MRI showed adenoma in two patients. Surgical and histopathological findings confirmed the diagnosis of ectopic parathyroid adenoma in nine patients. Sensitivity and specificity for ultrasound were 11 and 100%, respectively. 99mTc MIBI had sensitivity, specificity, positive and negative predictive values of 100, 86, 98 and 65%, respectively. The combination of 99mTc-MIBI with CT or MRI yielded the correct diagnosis in all cases, giving a sensitivity and specificity of 100%.

The incidence of ectopic parathyroid adenoma is much lower than previously reported. Multimodality imaging in a tertiary referral centre is the ideal approach for accurate diagnosis.