Parathyroid carcinoma is a rare cause of
primary hyperparathyroidism with rather poor prognosis. Apart from surgery, no evidence-based treatments exist. A 48-year-old woman presented with
weight loss,
nausea,
constipation, hypercalcemic crisis, and a recurrent neck
tumor 5 years after primary surgery of a parathyroid
tumor that primarily was classified as an
adenoma. Histopathological reevaluation of the original
tumor revealed the correct diagnosis to be
parathyroid carcinoma (PC). The patient underwent surgery of the recurrent
tumor, which was locally invasive with metastatic spread to the mediastinum and neck lymph nodes. Computed tomography demonstrated large lytic bone lesions in both iliac bones including, on the right, a soft tissue mass compatible with bone
metastasis. The patient was treated with
cinacalcet, repeated
zoledronic acid infusions, and
temozolomide cycles for 1 year. She underwent two additional neck surgeries for PC and
sternotomy for resection of mediastinal
metastases. Massive osteolytic lesions in both femoral necks caused imminent fracture risk and therefore both femurs were prophylactically stabilized by intramedullary nail. Serum
calcium normalized after the third neck surgery,
cinacalcet was discontinued, and
parathyroid hormone gradually normalized during continued treatments with
temozolomide,
adjuvant radiotherapy, and
zoledronic acid, with no signs of active disease on imaging and normal biochemistry. The patient remains in remission 17 years after successful combined treatments for recurrent, metastasized PC. The parathyroid
tumor tissue demonstrated high
O6-methylguanine DNA methyltransferase (MGMT) promoter methylation status, a known predictor of positive
temozolomide treatment response in other
tumors. In addition, synergistic effects of multiple treatments may have accounted for the favorable response. © 2018 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and
Mineral Research.