Background: Long-term severe hyperparathyroidism leads to thinning of cortical bone and cystic bone defects referred to as osteitis fibrosa cystica. Cysts filled with hemosiderin deposits may appear colored as "brown tumors." Osteitis fibrosa cystica and brown tumors are occasionally visualized as multiple, potentially corticalis-disrupting bone lesions mimicking metastases by bone scintigraphy or 18F-fluorodeoxyglucose positron emission tomography.
Case presentation: We report a case of a 72-year-old white woman who presented with malaise, weight loss, and hypercalcemia. She had a history of breast cancer 7 years before. The practitioner, suspecting bone metastases, initiated bone scintigraphy, which showed multiple bone lesions, and referred her to our hospital for further investigations. Laboratory investigations confirmed hypercalcemia but revealed a constellation of primary hyperparathyroidism and not hypercalcemia of malignancy; in the latter condition, a suppressed rather than an increased value of parathyroid hormone would have been expected. A parathyroid adenoma was found and surgically removed. The patient's postoperative course showed a hungry bone syndrome, and brown tumors were suspected. With the background of a previous breast cancer and lytic, partly corticalis-disrupting bone lesions, there was a great concern not to miss a concomitant malignant disease. Biopsies were not diagnostic for either malignancy or brown tumor. Six months after the patient's neck surgery, imaging showed healing of the bone lesions, and bone metastases could be excluded.
Conclusions: This case shows essential differential diagnosis in a patient with hypercalcemia and multiple bone lesions. Whenever multiple, fluorodeoxyglucose-avid bone lesions are found, malignancy and metabolic bone disease should both be included in the differential diagnosis. Fluorodeoxyglucose-avid and corticalis-disrupting lytic lesions also occur in benign bone disease. There may be very few similar cases with heterogeneous and widespread bone lesions reported in the literature, but we think our patient's case is particularly remarkable for its detailed imaging and the well-documented course.
Keywords: 18F-FDG-PET; Brown tumors; Hungry bone syndrome; Hypercalcemia; Lytic bone lesions; Osteitis fibrosa cystica; Primary hyperparathyroidism.