Unusual case of solitary functioning bone metastasis from a "parathyroid adenoma": imagiologic diagnosis and treatment with percutaneous vertebroplasty--case report and literature review.

BACKGROUND Parathyroid carcinoma is a rare endocrine malignancy that accounts for a small percentage of patients with primary hyperparathyroidism. Here, an unusual patient with parathyroid carcinoma misdiagnosed as a parathyroid adenoma was reported. A solitary L4 vertebral metastasis, which was localized by technetium-99m-labelled methoxyisobutyl isonitrile ((99m)Tc-MIBI) single photon emission computed tomography (SPECT)/computed tomography (CT) fusing images, was successfully treated with percutaneous vertebroplasty (PVP) for the first time. PATIENT AND METHODS A 53-year-old man with primary hyperparathyroidism and a palpable mass in the right neck was referred. A right unilateral parathyroidectomy was performed. A pathological diagnosis of parathyroid adenoma was made; however, hyperparathyroidism persisted with a serum calcium of 4.51 mmol/L and a PTH of 3235 pg/mL. Early and delayed images of the (99m)Tc-MIBI whole-body scan revealed abnormal (99m)Tc-uptake in the lower abdomen. The delayed (99m)Tc-MIBI SPECT/CT fusion images found that the lower abnormal (99m)Tc-MIBI uptake was located in the area of osteolytic destruction of the L4 vertebra. A bone metastasis from parathyroid carcinoma was diagnosed based on histopathological evaluation and immunohistochemical staining. PVP was performed to treat the osteolytic destruction of the L4 vertebra. The PTH level decreased to normal within 1 week after PVP. CONCLUSION (99m)Tc-MIBI SPECT/CT scan may be a useful and suitable method by which to localize functioning distant metastases from the parathyroid cancer when serum PTH and calcium levels remain greatly elevated after parathyroidectomy. PVP may be an effective procedure in eliminating cancer cells, reducing serum PTH levels, preventing bone fractures, and improving the quality of life of patients.