Bisphosphonate-related osteonecrosis and metastasis within the same site of the jaw

Osteonecrosis of the jaw (ONJ) is a well known complication in patients treated with bisphosphonates (BPs) for skeletal metastasis and multiple myeloma (MM). Few oncologic patients under treatment with BPs and with ONJ and metastasis or MM at the same site of the jaw have been described. We report here on a 54-year old white female who was treated with intra-venous zoledronic acid for skeletal metastasis of breast cancer who developed ONJ. Because of a fracture at the site of ONJ, resection of the affected segment was performed. Although metastasis was not suspected by pre-operative image analysis, histological examination revealed syncronous osteonecrosis and breast cancer metastasis in the resected mandibular segment. This case highlights that, in oncologic patients treated with BPs, ONJ may hide malignancy and that histology is the unique tool by which the diagnosis of either osteonecrosis or malignancy or both can be made definitely.