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An Unusual Retropharyngeal Lesion

Educational Objective
Based on this clinical scenario and the accompanying image, understand how to arrive at a correct diagnosis.
1 Credit CME

A female smoker in her 50s was referred for hyperparathyroidism and a multinodular goiter. The patient reported symptoms of joint and musculoskeletal pain and fatigue but denied fever, sore throat, abdominal pain, and kidney stones. Her medical history was remarkable for congestive heart failure and schizophrenia. Neck examination revealed no meaningful findings except right thyroid enlargement. Results of laboratory evaluation demonstrated normal white blood cell count, borderline hypercalcemia (10.6 mg/dL), and elevated parathyroid hormone level (208 pg/mL). She underwent ultrasonography at an outside facility, and results demonstrated a 2.2-cm dominant right thyroid nodule with additional smaller thyroid nodules. Findings of preoperative technetium-99m (Tc-99m) sestamibi planar and single-photon emission computed tomographic/computed tomographic (SPECT/CT) imaging (Figure, A) were nonlocalizing for a parathyroid adenoma and showed increased uptake in the dominant right thyroid nodule (Figure, B). Results of an ultrasound-guided biopsy of the thyroid nodule demonstrated a benign colloid nodule with cystic changes. Computed tomography with intravenous contrast was obtained, and findings were initially reported as negative except for right multinodular goiter. However, on additional review, a well-circumscribed fat density mass measuring 3.0 × 2.3 × 1.1-cm was identified in the right retropharyngeal space posterior to the hypopharynx (Figure, C).

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A. Ectopic parathyroid lipoadenoma

The patient underwent transcervical excision of the mass, located in the retropharyngeal space posterolateral to the right inferior constrictor muscle at the level of the hypopharynx. There was intraoperative normalization of parathyroid hormone levels, and final pathological results confirmed parathyroid lipoadenoma. Thus, to our knowledge, the present case is the first reported ectopic parathyroid lipoadenoma within the retropharyngeal space. In addition, this case demonstrates how parathyroid lipoadenomas are less reliably detected by Tc-99m SPECT/CT than their typical parathyroid adenoma counterparts, which highlights the value of contrasted CT.

Parathyroid lipoadenoma is a rare variant of parathyroid adenoma with a similar presentation owing to hyperfunctioning parathyroid tissue. The presence of increased fatty stroma differentiates parathyroid lipoadenoma from parathyroid adenoma and also renders it more difficult to identify on preoperative imaging. Although it is uncertain where the fatty stroma originates from, it has been postulated that the same factors that drive growth of parathyroid chief cells are also responsible for fatty growth. Obesity and advanced age may increase this percentage of fatty tissue. Only 70 cases of parathyroid lipoadenoma have been described to date,15 accounting for less than 1% of all cases of hyperparathyroidism, and most ectopic locations have been in the mediastinum.6 Of note, although a liposarcoma may have similar imaging findings to a lipoadenoma, corresponding primary hyperparathyroidism would be unlikely. The imaging characteristics are clearly not consistent with thyroid tissue. An isolated retropharyngeal abscess would be less likely without infectious symptoms as well.

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Article Information

Corresponding Author: Michael W. Sim, MD, Department of Otolaryngology–Head and Neck Surgery, Indiana University School of Medicine, 1130 W Michigan St, Ste 400, Indianapolis, IN 46202 (mwsim@iu.edu).

Published Online: September 17, 2020. doi:10.1001/jamaoto.2020.2703

Conflict of Interest Disclosures: None reported.

Additional Contributions: We thank the patient’s mother for granting permission to publish this information.

Hyrcza  MD , Sargın  P , Mete  O .  Parathyroid lipoadenoma: a clinicopathological diagnosis and possible trap for the unaware pathologist.   Endocr Pathol. 2016;27(1):34-41. doi:10.1007/s12022-015-9404-5 PubMedGoogle ScholarCrossref
Triviño  A , Varela  J , Ayllón  S .  Mediastinal parathyroid lipoadenoma.   Arch Bronconeumol. 2020;56(5):323. doi:10.1016/j.arbres.2019.04.016PubMedGoogle ScholarCrossref
Fujisawa  S , Inagaki  K , Wada  J .  Parathyroid lipoadenoma: a pitfall in preoperative localization.   Intern Med. 2019;58(8):1183-1184. doi:10.2169/internalmedicine.1249-18 PubMedGoogle ScholarCrossref
Özden  S , Güreşci  S , Saylam  B , Dağlar  G .  A rare cause of primary hyperparathyroidism: parathyroid lipoadenoma.   Auris Nasus Larynx. 2018;45(6):1245-1248. doi:10.1016/j.anl.2018.05.001 PubMedGoogle ScholarCrossref
Aggarwal  A , Wadhwa  R , Aggarwal  V .  Parathyroid lipoadenoma: a rare entity.   Indian J Endocrinol Metab. 2018;22(1):174-176. doi:10.4103/ijem.IJEM_273_17 PubMedGoogle ScholarCrossref
Gowda  K , Matippa  P.   Parathyroid lipoadenoma: a diagnostic pitfall during frozen section evaluation of parathyroid lesions.   Int Clin Pathol J. 2016; 3(2):193-194. doi:10.15406/icpjl.2016.03.00070 Google ScholarCrossref
Nguyen  BD .  Parathyroid imaging with Tc-99m sestamibi planar and SPECT scintigraphy.   Radiographics. 1999;19(3):601-614. doi:10.1148/radiographics.19.3.g99ma10601 PubMedGoogle ScholarCrossref
Alenezi  S , Asa’ad  S , Elgazzar  A.   Scintigraphic parathyroid imaging: concepts and new developments.   Res Rep Nucl Med. 2015;2015(5):9-18.Google Scholar
AMA CME Accreditation Information

Credit Designation Statement: The American Medical Association designates this Journal-based CME activity activity for a maximum of 1.00  AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Successful completion of this CME activity, which includes participation in the evaluation component, enables the participant to earn up to:

  • 1.00 Medical Knowledge MOC points in the American Board of Internal Medicine's (ABIM) Maintenance of Certification (MOC) program;;
  • 1.00 Self-Assessment points in the American Board of Otolaryngology – Head and Neck Surgery’s (ABOHNS) Continuing Certification program;
  • 1.00 MOC points in the American Board of Pediatrics’ (ABP) Maintenance of Certification (MOC) program;
  • 1.00 Lifelong Learning points in the American Board of Pathology’s (ABPath) Continuing Certification program; and
  • 1.00 CME points in the American Board of Surgery’s (ABS) Continuing Certification program

It is the CME activity provider's responsibility to submit participant completion information to ACCME for the purpose of granting MOC credit.

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