Primary Hyperparathyroidism Misdiagnosed as Giant Cell Bone Tumor of Maxillary Sinus

Primary hyperparathyroidism is an endocrine disorder recognized by hyperfunction of parathyroid gland, which can result in persistent bone absorption and brown tumor. Facial involvement of brown tumor is rare and usually involves the mandible. Giant cell tumor ( GCT) is an expansile osteolytic bone tumor which is very similar in clinical, radiological and histological features to brown tumor. Herein, we present a 35-year-old woman with an 11-month history of gradually swelling of the right maxilla and buccal spaces began during pregnancy two years ago. No other clinical or laboratory problems were detected. Postpartum CT scan demonstrated a lytic expansile multi-septated mass lesion containing enhancing areas, which initially described as GCT of the right maxillary sinus following surgery. Four months later, gradual progressive swelling of the bed of tumor was recurred and revised pathological slices were compatible with GCT. Regarding patient recent paresthesia, repeated laboratory tests were performed. Finally, according to laboratory results (elevation of serum calcium and parathyroid hormone), ultrasonographic findings and radioisotope scan (Sestamibi), probable parathyroid mass and brown tumor of maxilla was diagnosed. Pathology confirmed hyperplasia of right inferior parathyroid gland. Our case was thought-provoking due to its interesting clinical presentation and unusual presentation of brown tumor in parathyroid hyperplasia.