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SUN-505 The Invincible Parathyroid Gland

Abstract Background: Uncontrolled secondary hyperparathyroidism sometimes requires parathyroidectomy for control of parathyroid levels. We present a case of secondary hyperparathyroidism with recurrence due to hyperplasia of her re-implanted parathyroid gland and atypical features concerning for parathyroid carcinoma. Case Presentation: A 56 year old woman with a history of ESRD on peritoneal dialysis and gastric bypass surgery developed secondary hyperparathyroidism that required a parathyroidectomy with transplantation of a portion of her parathyroid gland in the right forearm in 2015. Surgical pathology showed four-gland hyperplasia. Following surgery, labs revealed a calcium of 8.6mg/dl and a PTH of 206 pg/ml. Subsequently, she developed hypocalcemia with a calcium of 5.7mg/dL, which was treated with calcitriol 2.5mcg three times daily, phoslo three times daily, and sensipar 90mg daily. Her PTH continued to rise from years 2015-2018, ranging between 1200- 1900 pg/ml. Labs in May 2018 revealed a calcium of 10.1 mg/dL, phosphorus of 9.0 mg/dL, and of PTH 1811 pg/ml. Physical exam showed a 4 cm mass in her right forearm at the site of parathyroid re-implantation. Due to inability to control her PTH and phosphorus levels, the re-implanted parathyroid tissue was removed and a small piece was re-implanted in the brachioradialis muscle in June 2018. Pathology demonstrated a 5.5x3x2cm mass with atypical parathyroid proliferation with necrosis and focal vascular invasion suspicious for parathyroid carcinoma. After surgery, PTH was 184 pg/ml and calcium was 5.4 mg/dL. The patient was referred to oncology for evaluation. CT chest was negative and ultrasound of the forearm showed a 6x2x5mm hypoechoic structure in the subcutaneous fat. The patient is currently maintained on calcium 1500mg four times a day, lanthanum, and calcitriol 7mcg divided four times a day. Most recent calcium was 8.4mg/dL and phosphorus was 5.9mg/dL. She will continue ultrasound surveillance of her forearm due to the atypical pathology of her re-implanted parathyroid tissue. Conclusion: We present a case of secondary hyperparathyroidism requiring parathyroidectomy with subsequent hyperplasia of the re-implanted parathyroid gland. A recent meta-analysis suggests that total parathyroidectomy may be preferred due to the risk of recurrence with total parathyroidectomy with autotransplantation (1). To our knowledge, there are no reported cases of a parathyroid carcinoma occurring in a re-implanted parathyroid gland. While this patient’s pathology was not definitely a parathyroid carcinoma, the pathology was atypical and concerning for malignancy. References: 1. Liu M, Qiu N, Zha S et al. Secondary Hyperparathyroidisim in chronic renal failure: A systematic review and meta-analysis. International Journal of Surgery. 2017; 44:353-362.