SAT203 Parathyroid Adenoma Masquerading As Parathyroid Carcinoma

Abstract Disclosure: M. Fariduddin: None. A. Lupieri: None. H.L. Calero: None. A. Rubenfeld: None. Y. Eisenberg: None. Case: 22 y/o pregnant female (5 weeks gestation) presented to the endocrinology clinic after a hospital admission for nausea, vomiting, constipation, fatigue and joint pain with labs showing calcium (corrected) of 14 mg/dL and PTH of 1200 pg/ml. Labs in the clinic showed calcium at 16 mg/dL and PTH 1500 pg/ml. She was re-admitted for IV fluids, calcitonin and zoledronic acid. Severe hypercalcemia, young age, and extremely high PTH levels were highly suggestive of parathyroid cancer. CT of neck showed a 2 cm right inferior parathyroid mass abutting the esophagus with concern for esophageal invasion with no evident plane between the mass and the esophagus. No cervical adenopathy was noted. Patient in conjunction with her obstetrician made an informed decision to terminate the pregnancy as this was an undesired pregnancy. She underwent an urgent right inferior gland parathyroidectomy. The mass was not fixed to underlying structures and was resected in-toto. Pathology showed chief cells with clear cytoplasm, and homogeneously round nuclei. There were no atypical mitoses, lymphovascular invasion, perineural invasion, or other invasive features concluding the final pathology as parathyroid adenoma. Discussion: Primary hyperparathyroidism predominantly affects postmenopausal women. Most common cause is parathyroid adenoma (80-85%). Parathyroid carcinoma is a rare cause of primary hyperparathyroidism (1-2%).80% people with parathyroid adenoma and primary hyperparathyroidism are diagnosed incidentally with mildly elevated calcium. PTH elevation is around 1.5-2 times the upper limit of normal. Symptoms are mild sequelae of hypercalcemia. PTH levels 5-10 times upper limit of normal, severe hypercalcemia (Ca > 14 mg/dl) or a hypercalcemia crisis are highly suspicious for parathyroid cancer. Surgical resection is the mainstay of treatment. Clinical criteria play a key role in early identification of parathyroid carcinoma in order to get these patients to surgery before tumor spread and improve long term survival. Our patient with significantly elevated calcium and parathyroid hormone had an atypical presentation of a parathyroid adenoma thus uncovering the limitations of clinical criteria in identifying a parathyroid carcinoma. Most of the patients with a parathyroid adenoma will eventually require surgery, however the technique, extent and urgency of surgery is affected based on clinical situations like these. The timing of the surgery could be detrimental when coupled with a scenario like our patient’s pregnancy wherein you could delay the surgery until the second trimester had the patient wanted to continue the pregnancy. This case highlights the importance of awareness of atypical presentations of parathyroid adenomas and to have a cautious approach in patients with clinical concern for parathyroid carcinoma especially if there is a potential benefit to delay surgery. Presentation: Saturday, June 17, 2023