Functional parathyroid carcinoma. Cytology, histology, and ultrastructure of a case

A case of a functional parathyroid carcinoma that recurred 1 year after being resected is presented. The clinical and laboratory data and the histologic structure are presented with confirmatory electron microscopy. The preoperative aspiration biopsy showed findings suggestive of parathyroid carcinoma although simultaneous core biopsy results were reported as parathyroid adenoma. The differential cytologic diagnosis with thyroid neoplasms is discussed.