Primary hyperparathyroidism (PHPT) due to parathyroid carcinoma is rare, and affects more frequently women in their 4th-5th decades of life. Parathyroid cancer (PC) accounts for 0.5% up to 5% of the patients with primary hyperparathyroidism (PHPT). Diagnosis of PC is not easy, and a lot of patients with PHPT receive no pre-operative or intra-operative diagnosis of malignancy. Most of PC are hyperfunctioning, with marked serum PTH levels, and symptoms occurs more frequently than in benign disease. We report the case of a 52 years old woman that underwent a single parathyroidectomy for hyperfunctioning gland. Histological examination revealed carcinoma. Parathyroid carcinoma is rare and surgery represent the only curative approach, although there can be a local recurrence of the disease. A pre-operative diagnosis is not easy, and many features that suggest the diagnosis of malignancy are controversial. According to the literature, we think that the cure of the parathyroid cancer is difficult to achieve. After two years of follow- up, our patient is in good conditions and has no evidence of disease. A careful follow up is of primary importance to diagnose the local recurrence of disease and perform a second surgical treatment, to achieve the control of hypercalcemia, which causes severe metabolic alterations and visceral lesions until the death.