SAT573 Incidental Discovery Of CHEK2 Mutation With Papillary Thyroid Cancer

Abstract Disclosure: F.L. Thelmo: None. A. Mehrab: None. S.A. Jabbour: None. A 66-year-old white male had been following steadily with our practice for greater than a decade where we were managing his post-ablative hypothyroidism from toxic multinodular goiter 20 years prior. Many years later, the patient developed hypercalcemia and was found to have asymptomatic primary hyperparathyroidism. He did not meet any indication for parathyroidectomy. In early January 2021, the patient was referred to a clinical geneticist at the behest of his wife as she was concerned that he had a very high rate of cancer in his family. The patient had a total of 11 relatives who either currently had or previously died from a malignancy, of which only one of them was on his maternal side. The patient’s father had a personal history of breast cancer, prostate cancer, and bone cancer at the time he passed away. The patient underwent a full panel of genetic testing and was found to be positive for a CHEK2 (Checkpoint Kinase 2) mutation. Around this time, the patient’s hypercalcemia escalated up to 13mg/dL without evidence of hypoalbuminemia. Decision was made to pursue surgery. In order to localize the parathyroid adenoma, a technetium sestamibi scan and a neck ultrasound were obtained. Sestamibi scan showed increased parathyroid adenomatous activity in the left lower portion of the thyroid bed and ultrasound confirmed the left lower pole parathyroid adenoma with a dominant hypoechoic 2.5cm TI-RADS 5 thyroid nodule which on biopsy was suspicious for papillary thyroid carcinoma. The patient underwent a total thyroidectomy in addition to the parathyroidectomy. Pathological evaluation confirmed a parathyroid adenoma and a classic variant of papillary thyroid carcinoma without angioinvasion and minimal extrathyroidal invasion classified as Stage 1 T2N0M0. The patient did not meet criteria for treatment with radioactive iodine and at the time of this writing is doing well, on levothyroxine with low-normal TSH and undetectable thyroglobulin with normal serum calcium. He has no other signs of malignancy at this time. However, given his CHEK2 mutation, he will require ongoing multi-disciplinary cancer surveillance. We would like to draw attention to this not uncommon oncogenic mutation that due to its incomplete penetrance does not always present such a staggering family history of cancer and thus may go undetected. CHEK2 mutations occur in roughly 1% of all individuals who undergo genetic evaluation for cancer. The mutation moderately increases the patient and their family’s risk for multiple malignancies including: breast, thyroid, prostate, stomach, kidney, and plasma cell malignancies. Individuals with this mutation should be screened thoroughly by a multi-disciplinary team based on the severity of their inherited mutation. These individuals should also receive counseling on family planning if conception is desired. Presentation: Saturday, June 17, 2023