Primary hyperparathyroidism-induced brown tumors caused by parathyroid carcinoma: a case report and literature review

Brown tumors represent a benign disease that is induced by primary or secondary hyperparathyroidism, with the pathological feature of osteitis fibrosa cystica. Primary hyperparathyroidism caused by parathyroid carcinoma resulting in brown tumors is extremely rare. Herein, we report the case of a 60-year-old male patient who was admitted for giant cell tumors of the bone with local pain and limited movement of the left knee joint. With early detection of multifocal osteolytic bone lesions, hyperparathyroidism (parathyroid hormone: 2365.00 pg/mL), and parathyroid cancer, the diagnosis of brown tumors was confirmed without any unnecessary or harmful interventions. Thereafter, he underwent parathyroidectomy, from which postoperative pathology confirmed parathyroid carcinoma, and total knee arthroplasty to restore movement of the knee joint. Seven months after surgery, the left knee joint had good range of movement. This case emphasizes that detecting patients' parathyroid hormone levels should not be neglected when diagnosing multifocal osteolytic bone lesions. A comprehensive analysis combining clinical symptoms, imaging, and laboratory tests is conducive to accurate disease assessments and avoiding unnecessary or even survival-impairing surgery. However, when the tumor involves a large joint or seriously affects joint movement, surgery may be worth considering.