title: Incidence and localization of ectopic parathyroid adenomas in previously unexplored patients.
abstract: BACKGROUND
  Parathyroidectomy has a success rate of >95 % for cure of primary hyperparathyroidism. In about 6-16 % of cases, one or more hyperfunctioning parathyroid gland(s) are found in an ectopic location. Accurate preoperative imaging can aid in detecting these ectopically located glands and allow a focused surgical approach with an even higher success rate. The objective of this study was to assess the utility of ultrasonography (US) and technetium-99m-sestamibi (MIBI) scans in locating ectopic parathyroid glands in previously unexplored patients who presented with primary hyperparathyroidism.
  
  
  METHODS
  We analyzed a total of 1,562 patients who underwent surgery for hyperparathyroidism at our institution from 2000 to 2010. Ectopic parathyroid adenomas were identified in 346 of the patients (22 %). Of the 346 patients, we excluded 144 who underwent reoperations, had four-gland hyperplasia or were missing imaging details. We carefully reviewed the data, including demographics, laboratory values, preoperative localizing imaging details, and operative findings. Preoperative US and MIBI results were compared to the intraoperative findings.
  
  
  RESULTS
  We analyzed 202 patients with ectopic glands for accuracy of preoperative localization. Of these 202 patients, a single adenoma was the most common (89 %) followed by double adenoma (11 %). The ectopic parathyroid glands were predominantly located in the thymus (38 %) followed by 31 % in the retroesophageal region; 18 % were intrathyroidal. Preoperative MIBI scans had a sensitivity of 89 % (161/197), whereas US had a sensitivity of 59 % (35/63) for detecting ectopic glands. Overall, both imaging modalities had a positive predictive value of 90 %, with MIBI correctly predicting ectopic glands best in the thymus, mediastinum, or the retroesophageal space, and US was most accurate at detecting intrathyroidal glands.
  
  
  CONCLUSIONS
  Based on the data available at our institution, MIBI has a higher sensitivity than US in correctly localizing ectopic parathyroid adenomas, but the accuracy of detection varies based on location. Both imaging techniques have a high PPV for detecting an ectopic gland. Therefore, imaging with MIBI and US can be complementary, and positive localization of an ectopic gland with either modality is highly accurate and can facilitate a more focused surgical approach.
authors.affiliation: Section of Plastic and Reconstructive Surgery, Department of Surgery, University of Wisconsin, 3028 Wisconsin Institute of Medical Research, 1111 Highland Avenue, Madison, WI 53705, USA. miroy@wisc.edu
authors.forename: Madhuchhanda
authors.initials: M
authors.lastname: Roy
authors.forename: Haggi
authors.initials: H
authors.lastname: Mazeh
authors.forename: Herbert
authors.initials: H
authors.lastname: Chen
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Sippel
mesh_terms: D000236:Adenoma / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology*; D002828:Choristoma / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010280:Parathyroid Glands; D010282:Parathyroid Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012189:Retrospective Studies; D017256:Technetium Tc 99m Sestamibi; D014463:Ultrasonography
chemical_list: D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi