Ectopic Parathyroid Adenoma in Piriform Sinus: Case Report and Review of the Literature.

During routine blood work, a 53-year-old female patient was noted to have asymptomatic hypercalcemia and subsequently found to have hyperparathyroidism. Localization studies for a suspected parathyroid adenoma included 99mTc Sestamibi scintigraphy, Single Photon Emission Computed Tomography (SPECT)/computed tomography (CT) study, and ultrasound of the neck, which were initially read as negative for parathyroid adenoma. A contrast-enhanced CT scan of the neck was performed to locate the suspected parathyroid adenoma and demonstrated a soft tissue lesion within the right piriform sinus. Flexible fiber optic nasolaryngoscopy revealed a submucosal lesion in the right piriform sinus. Following these findings, the initial 99mTc Sestamibi scintigraphy and SPECT/CT were reviewed with confirmation of a focal area of increased activity superior to the right thyroid lobe, corresponding to a nodule in the right piriform sinus that demonstrated increased activity on SPECT/CT. The patient was brought to the operating room for surgical management where a laryngoscope and operating microscope were utilized. The encapsulated lesion was dissected and excised in total. The parathyroid hormone and ionized calcium levels normalized postoperatively. Pathology confirmed a parathyroid adenoma. Parathyroid adenomas are the most common cause of primary hyperparathyroidism. Sixteen percent of parathyroid adenomas can be situated in an ectopic location. Ectopic parathyroid adenomas in the piriform sinus are rare with only a few previously documented cases. We document a rare case of ectopic parathyroid adenoma in the piriform sinus overlooked on initial imaging studies. These lesions can be challenging to localize, however, an understanding of embryology, close scrutiny of possible ectopic locations, and the application of complementary imaging techniques may prove useful for surgeons and clinicians.