Medullary thyroid cancer with RET V804M mutation: more indolent than expected?

Significant genotype-phenotype variability among multiple endocrine neoplasia type 2A patients with a RET V804M mutation has been reported.

Patients with a RET V804M mutation treated at a single center were identified (January 1996-December 2020). The baseline characteristics, operative details, pathology, biochemical, and long-term data were analyzed.

There were 79 patients; none developed pheochromocytoma or hyperparathyroidism or died in the study period. The mean age was 41.5 years (range = 1.0-81.0 years); 46.8% were men. Of 68 surgical patients, 53 (77.9%) underwent total thyroidectomy and 15 (22.1%) underwent total thyroidectomy with central neck dissection with or without lateral neck dissection. Twenty-four patients had elevated preoperative calcitonin, of whom 12 underwent total thyroidectomy (median = 7.5; range = 5.0-237.0 pg/mL), 10 underwent total thyroidectomy + central neck dissection (median = 27.6; range = 5.1-147.0 pg/mL), and 2 underwent total thyroidectomy + central neck dissection + lateral neck dissection (median = 3182.0; range = 361.0-6003.0 pg/mL). Pathology was benign (27.9%), papillary thyroid cancer alone (1.5%), C-cell hyperplasia (23.5%), and medullary thyroid cancer (47.1%; median tumor size = 3.0 mm). Three patients had elevated calcitonin postoperatively (median follow-up time = 60.0 months). In adjusted modeling, a preoperative calcitonin >5 pg/mL was associated with having medullary thyroid cancer on final pathology (odds ratio = 13.3; 95% confidence interval, 3.2-56.3; P < .001).

In this large United States cohort of surgical patients with a RET V804M mutation, most had indolent disease and were without classic multiple endocrine neoplasia type 2A features. Calcitonin >5 pg/mL may serve as a meaningful value to guide surveillance and timing of surgery.