Parathyroid adenoma presenting as a middle mediastinal mass in a patient with renal osteodystrophy and unclassified renal tumor

Abstract

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Learning Objectives: 1. Recognize the presentations of parathyroid adenomas in the thorax by Tc99m-sestamibi dual-phase parathyroid scintigraphy. 2. Recognize the pattern differences of renal osteodystrophy to that of metastatic bone disease by Tc99m-HDP whole-body bone scintigraphy.

Abstract Body: 63 year-old female presented at the ED with fatigue and weakness for over one year. Physical examination was remarkable for enlargement of the right thyroid lobe and a mass in her right leg. Laboratory tests were remarkable for anemia; TSH level was normal, BUN 137 mg/dL, serum creatinine 9.3 mg/dL, low bicarbonate, hyperglycemia, serum calcium 11.0 mg/dL, and serum alkaline phosphatase 608 mU/mL. Abdominal CT scan revealed atrophic kidneys with a large solid contrast-enhancing mass in the lower left kidney pole with bilateral nephrolithiasis and bilateral adrenal gland enlargement. Intact PTH molecule was 4,168 pg/mL, PTH-related peptide < 0.2 pg/mL; VMA and VHA levels were normal. Needle biopsy of the kidney mass was positive for unclassified neoplasm. CT scan of the thorax revealed a 30-mm contrast-enhancing mass posterior to the proximal trachea, a multinodular goiter, and diffuse osteolytic lesions. Tc99m-HDP whole-body bone scintigraphy revealed increased diffuse and focal uptake involving axial and appendicular skeleton, kidneys were poorly visualized. Tc99m-sestamibi dual-phase parathyroid scintigraphy showed abnormal increased uptake involving the middle and inferior right thyroid bed extending into the mediastinum which was persistent in the delayed phase. Findings were consistent with renal osteodystrophy, and brown tumors (BTs) with parathyroid adenoma (PA). A PA was found at needle core biopsy of the mediastinal mass. BTs (osteitis fibrosa cystica) are a rare clinical consequence of untreated severe primary or secondary hyperparathyroidism that may mimic metastatic bone disease. The routine use of one or more localizing studies commonly identifies the parathyroid tumor in patients with single-gland disease. Parathyroid scintigraphy using a single radionuclide with sestamibi correctly detects and localizes parathyroid adenomas.