A Rare Case of Parathyroid Carcinoma Initially Misdiagnosed as a Parathyroid Adenoma.

Parathyroid carcinoma is an uncommon endocrine malignancy that can resemble a benign parathyroid adenoma, typically presenting with hypercalcaemia and nonspecific symptoms that make preoperative diagnosis difficult. We report the case of a 38-year-old woman from Birmingham, United Kingdom, who presented with recurrent hypercalcaemia associated with body aches, lethargy, polydipsia, and voice changes. Initial laboratory tests revealed elevated calcium and elevated parathyroid hormone levels. Imaging studies identified a small left parathyroid lesion consistent with a functioning adenoma. The patient underwent left superior parathyroidectomy, with postoperative normalization of calcium and parathyroid hormone levels. Histopathological examination unexpectedly revealed parathyroid carcinoma, confirmed by parafibromin immunohistochemistry and review by a second pathologist. Postoperative imaging showed no evidence of metastasis, and the patient remains asymptomatic with normal biochemical values during follow-up. This case highlights the diagnostic challenge of distinguishing parathyroid carcinoma from adenoma and emphasizes the importance of histopathological evaluation and multidisciplinary management.