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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,1- 5 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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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 (email@example.com).
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.
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