Presumed Familial Late-Onset Medullary Thyroid Cancer in a patient with a germline point mutation, c. 2304 G->T, in RET proto-oncogene codon 768: specific mutation may guide timing of prophylactic total thyroidectomy in affected family members

A 54-year-old woman presented for unintentional weight loss. Her primary care physician detected a thyroid lesion on physical examination. Neck ultrasound showed a right 1.4 cm nodule with microcalcifications, a 1.4 cm extrathyroidal mass, and other hypoechoic nodules. FNA revealed medullary thyroid cancer. Preoperative CT scans of the chest, abdomen, and pelvis were negative. Preoperative calcitonin and CEA were elevated at 1743 pg/mL and 64.3 ng/mL respectively. Plasma free metanephrines, PTH, and calcium were normal. TSH was 5.81 mIU/L. There was no family history of MEN, adrenal disease, thyroid cancer, or calcium disorders. She underwent total thyroidectomy with bilateral LN dissection. The right laryngeal nerve was encased in tumor. Pathology showed multifocal MTC with bilateral involved lymph nodes, the largest of which was 1.5 cm. Perineural and angiolymphatic invasion was seen. Ten days postoperatively, calcitonin was 176 pg/mL. Seven months postoperatively, calcitonin was 146 pg/mL and CEA was 6.2 ng/mL.