Diagnostic Dilemma: A Case of Non-Functional Parathyroid Carcinoma Masquerading as a Thyroid Nodule

Non-functional parathyroid carcinoma (NFPC) is a rare, aggressive malignancy defined by the lack of parathyroid hormone (PTH) secretion. Its subtle clinical presentation often leads to diagnostic delays. A 51-year-old woman presented with a solitary thyroid nodule and an isolated mild elevation of PTH. Initially misdiagnosed with a benign thyroid lesion, she underwent a right thyroid lobectomy. Intraoperative suspicion and subsequent definitive histopathology confirmed the diagnosis of parathyroid carcinoma. This case underscores the critical importance of investigating even mild PTH elevation in patients with thyroid nodules, especially when fine-needle aspiration cytology (FNAC) yields inconclusive or benign results. It also illustrates the potential role of adjunctive techniques, such as multimodal imaging in guiding surgical strategy. Early and accurate diagnosis of NFPC is paramount, as timely intervention significantly influences prognosis. Clinicians should maintain a high index of suspicion for NFPC in the presence of thyroid abnormalities coupled with abnormal PTH levels to facilitate prompt diagnosis and optimal management.