Negative imaging studies for primary hyperparathyroidism are unavoidable: Correlation of sestamibi and high-resolution ultrasound scanning with histological analysis in 150 patients

Background: Preoperative localization studies with Tc-99m-sestamibi have become an integral step in the preoperative assessment of patients with primary hyperparathyroidism (PHPT). This enables scan-directed minimally invasive parathyroidectomy (MIP) to be the preferred treatment for PHPT in many units. This study aimed to identify factors that lead to negative imaging studies in patients with PHPT. Methods: Over a 3-year period consecutive unselected patients with PHPT underwent Tc-99m-sestamibi scanning and high-resolution ultrasound (US) scanning by the same radiologist. When localization studies were concordant, patients underwent MIP. Those patients with negative imaging studies underwent bilateral neck exploration. Histology slides were independently reviewed and the proportion of chief cells and oxyphil cells within each adenoma was estimated. Results: One hundred and fifty-eight patients underwent localization studies (38 men and120 women, aged 61.8 +/- 15.2 years). Sestamibi scans were negative in 52 (32%) and positive in 106 (68%) patients. There was a higher incidence of hyperplasia in the group of patients with negative sestamibi scans (4 out of 52 vs. 4 out of 103, P < 0.05, chi(2) test). In patients with negative sestamibi scans the majority of adenomas were formed predominantly from chief cells (26 out of 36) while the majority of patients with adenomas composed predominantly of oxyphil cells had positive scans (21 out of 23) (P < 0.05, chi(2) test). The weight of parathyroid adenomas was higher when sestamibi scans were positive (median: 1,180 vs. 517 mg, P < 0.05, Student's t-test). Conclusion: Successful preoperative localization of parathyroid adenomas using Tc-99m-sestamibi scanning is influenced by the cytological predominance of individual tumors. Negative scans might therefore be unavoidable in a subgroup of patients.