ACTA ENDOCRINOLOGICA (BUC)

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Background. Primary hyperparathyroidism (PHPT) is caused most commonly by a solitary adenoma and less commonly by multiglandular hyperplasia of the parathyroid glands (MGD). Minimally invasive parathyroidectomy (MIP) has become a frequently used strategy, but there are limitations to current preoperative localization techniques. Results. We report the case of a patient, 63 years old, female, with clinical and biochemical features of primary hyperparathyroidism (total serum calcium: 10.1mg/dL; PTH: 171pg/mL). Neck ultrasonography (USG) revealed a mixed hypoechoic tumor along the posterior aspect of the left thyroid lobe of 1.54x0.78 cm, being difficult to say if it was intrathyroidal or not. There was only minimal residual uptake in the left thyroid lobe at 4 h on Tc99m sestamibi imaging. She underwent USG-guided fine-needle aspiration (FNA) of the suspected tumor followed by PTH measurement from the needle washing (FNA-PTH). The cytology was non-diagnostic but the level of PTH in the aspirated fluid was 10.000 pg/ mL. The patient underwent an en bloc resection of the left thyroid lobe and the tumor, which was curative, as calcium (8.9 mg/dL) and PTH (25.52 pg/mL) decreased from the first day after surgery. Histopathology of the surgical specimen revealed a left parathyroid adenoma made of chief cells and included in the thyroid capsule together with the entire left thyroid lobe. Conclusion. This case report highlights the importance of FNA-PTH in the localization of functionally parathyroid tissue in difficult cases, where a clear target exists.