Summary

Carcinoembryonic antigen (CEA) is still the most widely used tumour marker for gastrointestinal cancer. CEA was originally thought to be a specific marker for colorectal cancer, but it turned out to be a non-specific marker for further studies. CEA levels can be elevated in breast, lung and liver cancers, among others, including medullary thyroid cancer. The authors report a case of a 73-year-old woman who had a right hemicolectomy for an ascending colon adenocarcinoma and showed a persistent elevation in the CEA marker during follow-up. After several imaging tests, recurrence of the colon cancer was not found, but the presence of thyroid nodules had been detected. The diagnosis of a medullary thyroid carcinoma was made after the finding of a high value of calcitonin. The patient had a total thyroidectomy with resection of the central and lateral lymph nodes.