AbstractPurposeTo investigate the value of ultrasound and serum marker tests in detecting lateral lymph node metastasis in medullary thyroid cancer (MTC).MethodsData of 105 patients diagnosed with MTC and admitted to the Department of General Surgery in Peking Union Medical College Hospital from June 2010 to August 2020 were collected and retrospectively analyzed.ResultsUltrasound examination alone had a sensitivity of 89.36% and a specificity of 70.69%. For surveillance of postoperative carcinoembryonic antigen and calcitonin, cut‐off values of 7.115 ng/mL and 13.185 pg/mL, respectively, were shown to discriminate the presence of cervical lymph node metastasis. Combining ultrasound and postoperative serum levels of both carcinoembryonic antigen and calcitonin as serial tests increased the specificity to 91.38% and 87.93%, with a sensitivity of 95.45%. Multivariate logistic analysis identified the following risk factors for lateral lymph node metastasis in MTC: suspicious lymph nodes detected by ultrasound and postoperative calcitonin above 13.185 pg/mL.ConclusionThe combination of ultrasound and serological tests achieved higher sensitivity and specificity to identify MTC cases with potential occult lateral cervical lymph node metastasis compared with single tests.