Positron emission tomography/computed tomography imaging of brown tumors mimicking multiple skeletal metastases in patient with primary hyperparathyroidism.

Brown tumors of bone are highly vascular, lytic bone lesions representing a reparative cellular process rather than a neoplastic process usually seen in patients with hyperparathyroidism. These tumors can behave aggressively and be destructive. We report a 49-year-old male patient who was admitted to our hospital with a long-term history of right shoulder and right hip pain. Multiple lytic and destructive bone lesions were found in X-ray graphy and CT images. These bone lesions mimicked multiple skeletal metastatic lesions and seemed to be those of the terminal stage of malignancy. PET scan was requested for the evaluation of FDG uptake of these lesions and to search the unknown primary tumor site. Positron emission tomography/computed tomography (PET/CT) images showed multiple hypermetabolic malignant or metastatic FDG avid bone lesions in skeletal system. However the biopsy results revealed no signs of malignancy and laboratory data showed elevated serum calcium, alkaline phosphatase, parathyroid hormone, low serum phosphate and parathyroid scintigraphy was performed. Adenoma in the left parathyroid gland was seen with Tc-99m MIBI parathyroid scintigraphy. Pathological results confirmed the diagnosis of parathyroid adenoma. Brown tumor is the potential cause of false-positive result in evaluation of a patient for unknown primary tumor or skeletal metastases with PET/CT imaging.