Huge brown tumor of the rib in an unlocatable hyperparathyroidism patient with "self-recovered" serum calcium and parathyroid hormone: A case report.

Background: The brown tumor is a kind of complication of hyperparathyroidism (HPT). The ultimate therapy usually is the resolution of HPT. We herein report an unlocatable HPT patient who received resection of a huge brown tumor of the rib, and experienced "self-recovery" of serum calcium and parathyroid hormone.

Case Summary: A 34-year-old female patient who suffered from a gradually increasing mass of the left chest wall since 2007 came to our hospital for treatment. The patient had a history of serum Ca and parathyroid hormone (PTH) increasing since June 2015 and received zoledronic acid treatment for 17 mo. When she came to our hospital in November 2017 after discontinuing medical treatment for 3 mo, the serum Ca and PTH levels were within normal ranges. The patient had no imaging abnormalities of parathyroid ultrasound or Tc-methoxyisobutyl isonitrile. Enhanced computed tomography revealed a local soft tissue mass of 96 mm × 113 mm with bone erosion of the left 8 rib, and the mass presented irregular enhancement with an unclear boundary between the mass and spleen. The mass was thought to likely be caused by HPT, but a malignancy could not be ruled out. Resection of the mass was performed, and the pathology proved that the mass was a brown tumor. A diagnosis of unlocatable HPT was considered. Since the serum Ca and PTH levels were both normal pre- and post-operation, the patient did not receive exploratory surgery for HPT, and received regular follow-up.

Conclusion: The huge brown tumor of the rib and "self-recovered" serum PTH and Ca levels are relatively rare in HPT patients. An exploratory operation may be deferred for these patients, and long-term follow-up should be performed.