Disseminated Brown Tumors from Hyperparathyroidism Masquerading as Metastatic Cancer: A Complication of Parathyroid Carcinoma

Abstract

Osteitis fibrosa cystica (brown tumors) can be a skeletal manifestation of advanced hyperparathyroidism, including parathyroid cancer. Severe osteitis fibrosa cystica can mimic metastatic bone diseases especially in patients with a history of cancer. Because the treatment and prognosis of these two problems differ greatly considering hyperparathyroidism in the differential diagnosis of patients found to have osteolytic lesions is critical for the appropriate management of these patients. In this case report we describe a patient with a history of renal cell cancer and presumed osteolytic bone metastases. During prophylactic intramedullary rodding to prevent pathologic fracture of her femur she was found to have a benign lesion related to her previously undiagnosed hyperparathyroidism caused by an underlying parathyroid cancer. A detailed review of this disease and the associated bone changes is also included to underscore the importance of an adequate differential diagnosis as well as optimal management. Patients with hypercalcemia or bony lesions should not automatically be treated palliatively for metastatic disease just because of a past medical history of cancer. Hyperparathyroidism is a readily curable problem if properly diagnosed.

A Young Man With Hypercalcemia

“…Osteitis fibrosa cystica can resemble metastatic parathyroid carcinoma, primary bone tumors, or multiple myeloma, both clinically and radiographically, with extremely elevated PTH levels and lytic bone lesions . Thus, clinicians should entertain a careful differential diagnosis and with consideration of both disease processes.…”

“…Osteitis fibrosa cystica can resemble metastatic parathyroid carcinoma, primary bone tumors, or multiple myeloma, both clinically and radiographically, with extremely elevated PTH levels and lytic bone lesions. 2,5,6 Thus, clinicians should entertain a careful differential diagnosisandwithconsiderationofbothdiseaseprocesses.Ofnote,both primaryandsecondaryhyperparathyroidismcanleadtoosteitisfibrosa cystica. Key features to distinguish primary from secondary hyperparathyroidism include evidence of renal dysfunction, generally lower calcium levels with correspondingly elevated PTH level, lower vitamin D levels, and decreased urinary calcium excretion.…”