SAT-352 Severe Primary Hyperparathyroidism, Hypercalcemic Crisis, Acute Pancreatitis and Fatality: Complications of Atypical Parathyroid Adenoma, a Case Report

BACKGROUND: Atypical parathyroid adenomas (APAs) are a controversial and rare entity. These tumors show some features of carcinomas including adherence to adjacent structures, banding fibrosis, mitotic activity, and tumor cells trapped within capsule; however, they lack definitive capsular, vascular, or perineural invasion. Patients are often asymptomatic, or have vague symptoms such as fatigue. Studies and literature have reported that the elevation in parathyroid hormone (PTH) and calcium levels in APAs are intermediate between those of adenomas and carcinomas, and that the clinical course is generally benign. Clinical Case: A 41-year old woman with diabetes mellitus, Hashimoto’s thyroiditis, and obesity was noted to have mild asymptomatic hypercalcemia during routine tests performed at an outside hospital several months prior to presentation. A few weeks prior to presentation, she started complaining of anorexia, nausea, vomiting and abdominal pain. At the time of presentation, she was critically-ill with a picture of severe acute pancreatitis. Laboratory tests showed hypercalcemia (13.9 mg/dL, normal 8.5-10.6 mg/dL) and elevated lipase (1134 U/L, normal 13-60 U/L); however, a magnetic resonance cholangiopancreatography showed no biliary obstruction. Further testing revealed markedly elevated PTH (>5000 pg/ml, normal 15-65 pg/ml), and subsequent neck ultrasound showed a solitary mass on the left side of the neck. Despite maximum medical treatment, the patient continued to rapidly decompensate and passed away rapidly. Autopsy examination revealed a picture of severe acute pancreatitis including a markedly enlarged necrotic pancreas (360 grams, normal: 60-100 grams), extensive omental fat necrosis, ascites, and dusky discoloration of the abdominal organs. A well-circumscribed mass (6.6 x 3.5 x 1.5 cm) was found on the superior aspect of the left thyroid lobe. The tumor showed parathyroid cell proliferation admixed with banding fibrosis, no unequivocal invasion into the surrounding capsule, blood vessels or perineural spaces, and no evidence of lymph node involvement or distant metastasis, consistent with a diagnosis of APA. Her cause of death was the left neck APA and its associated sequelae of significant hypercalcemia and acute pancreatitis. Conclusion: This patient had asymptomatic hypercalcemia for months prior to presentation with PTH/hypercalcemic crisis, highlighting the importance of ruling out primary hyperparathyroidism in the assessment of patients with asymptomatic hypercalcemia. While it’s generally appreciated that parathyroid carcinomas usually cause more profound hypercalcemia and are more likely to cause fatality from metabolic complications, and that APAs follow a generally more benign course, this case shows that APAs can grow into significantly large lesions and could follow a severe and abrupt clinical course if not surgically removed.