Ultrasound features of malignancy in the preoperative diagnosis of parathyroid cancer: a retrospective analysis of parathyroid tumours larger than 15 mm

Nearly all reported parathyroid cancers are > 15 mm at presentation. The objective was to identify ultrasound criteria of malignancy in parathyroid lesions of > 15 mm in size. This study was approved by a local ethics committee. A retrospective review of patients identified from a database from 2004-2009 was performed. All patients underwent ultrasound imaging according to the protocol. Two trained observers categorized findings using the pre-determined features: shape, calcification, pattern of vascularity, local infiltration and internal lesion gray scale appearances. Sixty-nine patients (mean age 54.3 years, range 19-79 years; male = 16, female = 53) fulfilled the criteria of a parathyroid lesion > 15 mm; 8/69 (11.6%) with parathyroid cancer and 61/69 (88.4%) with benign solitary parathyroid adenoma. A high positive predictive value (PPV) for cancer was identified for infiltration (PPV 100%) and calcification (PPV 100%), whilst a high negative predictive value (NPV) was found for the absence of suspicious vascularity (NPV 97.6%), a thick capsule (NPV 96.7) and inhomogeneity (NPV 100%). In lesions > 15 mm systematic ultrasound assessment of specific features provides a valuable tool to identify parathyroid cancers before surgery.