Atypical Parathyroid Adenoma with Multiple Brown Tumors as Initial Presentation: A Rare Entity.

Brown tumors seen in hyperparathyroidism are rare, non-neoplastic lesions because of abnormal bone metabolism, and they can mimic benign bone tumors or malignancy. Although biopsy is considered as the gold standard for diagnosis, it can be inconclusive. As the diagnosis of brown tumors is often challenging, a high index of suspicion is essential for diagnosis. We present a case of 21-year-old woman who presented with multiple painful bony lesions, which were initially misdiagnosed as fibrous dysplasia. Due to persistent bone pain and deterioration in her physical mobility, she was referred to tertiary care centre. After thorough clinical workup, she underwent Tc-99m methylene diphosphonate bone scintigraphy that raised strong clinical suspicion of hyperparathyroidism and brown tumors. Subsequently, Tc-99m-methoxy isobutyl isonitrile (MIBI) parathyroid scintigraphy revealed a solitary MIBI avid focal lesion, suggestive of left inferior parathyroid adenoma. Later parathyroidectomy was performed and histopathological examination confirmed it as atypical parathyroid adenoma.