Alencar R, et al. - In this retrospective review, researchers explored if carbohydrate antigen 19-9 (CA19-9) serum levels could predict medullary thyroid carcinoma (MTC) outcomes. From 1985 to 2017, they analyzed 122 MTC patients followed in a tertiary cancer center. For this investigation, clinical-pathological features, therapeutic approaches, and results have been documented. In those with disease progression, CA19-9 was significantly higher vs those without; patients who died from MTC also had higher CA19-9 levels. In addition to calcitonin and carcinoembryonic antigen, CA19-9 could play a role in metastatic MTC as a prognosticator.