PTH and nephrocalcinosis: Based on the three patients and the literature, the possibility of malignant pHPT should be considered when the following clinical features exist: (a) markedly elevated calcium levels typically above 3 mmol/L (17); (b) PTH levels above 3 to 10 times the upper limit of normal (3, 18, 19); (c) a palpable neck mass with a lesion >30 mm (20); (d) severe symptoms of bone (osteitis fibrosa cystica) disease and renal disease (renal stones and nephrocalcinosis) (3, 18); and (e) large, inhomogeneous, hypoechoic, and lobulated masses on ultrasonography.