SAT-364 Brown Tumor of the Mandible in Severe Uncontrolled Primary Hyperparathyroidism

Background: Brown tumors are a part of the complex “osteitis fibrosa cystica” which is a diffuse resorptive process of the bone resulting from uncontrolled hyperparathyroidism. Although these brown tumors were fairly common in the past(1), the incidence of brown tumors is now extremely rare in the United States due to early diagnosis and treatment of hyperparathyroidism. Here we describe an unusual presentation for osteitis fibrosa cystica. Clinical Case: A 38 year old woman was admitted to the hospital with rapidly growing facial swelling in June 2019. The swelling initially appeared in January 2019 and had rapidly increased in size since April 2019. The mass was malodorous, painful and interfered with oral intake. The patient smoked 1 pack per day for 13 years. A CT scan of the head and neck with contrast showed a 3.6 x 4.5 x 3.3 cm mass destroying the right mandibular body, involving the right platysma muscle and displacing the central and lateral incisor teeth and was concerning for malignancy. The initial impression was that this was likely a squamous cell carcinoma with local and perhaps distant metastases, complicated by humoral hypercalcemia of malignancy and she was admitted for management. Upon admission, her calcium level was 14 mg/dL, albumin 4.1 g/dL, phosphorus 1.4 mg/dL PTH level was 890 pg/mL and vitamin D level was 22 ng/mL. Since the high PTH did not fit with hypercalcemia of malignancy, further evaluation was undertaken. A thyroid ultrasound showed a 4.6 x 1.8 x 1.5 cm isoechoic, heterogeneous lesion in the left lower pole, and Tc-99 sestamibi scan suggested parathyroid origin. The biopsy of the mouth lesion showed fibro histiocytic proliferation with multiple giant cells, negative for malignancy and consistent with a brown tumor. CT scan of the chest, abdomen and pelvis did not reveal any other masses or lytic lesions. . A skeletal survey showed another 2 cm lytic lesion in the proximal left humeral metaphysis which was not biopsied. On parathyroidectomy, the patient was found to have an enlarged left inferior parathyroid gland measuring 3.3 x 3.0 x 0.8 cm weighing 7.093 grams. Intraoperatively PTH level decreased from 890 pg/mL to 69 pg/mL. Her calcium levels returned to normal post-operatively and she was discharged home. Pathologic examination report revealed the mass to be a parathyroid adenoma. The patient reports a reduction in the size of her mandible mass since the surgery. Conclusion: Although uncommon, brown tumors can be seen in uncontrolled primary hyperparathyroidism. The mandible is a common site, though, as in this case, it is less common for it to be the only site affected Reference: 1. Rosenberg, E. H. (1962). Hyperparathyroidism. A review of 220 proved cases with special emphasis on findings in the jaws. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 15(2), 84–94.