{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,28]],"date-time":"2025-10-28T17:58:40Z","timestamp":1761674320427,"version":"build-2065373602"},"reference-count":41,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2021,8,5]],"date-time":"2021-08-05T00:00:00Z","timestamp":1628121600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Current Oncology"],"abstract":"<jats:p>Serum carcinoembryonic antigen (CEA) is a tumor marker especially used to follow a patient with colorectal cancer. However, it is non-specific and could be increased in several cancers and some benign conditions. We report the case of a 70-year-old man followed since 2014 for a left colon adenocarcinoma with the persistence of an increased CEA. There was no evidence of recurrence, but a right lobar thyroid nodule without a significantly increased uptake was incidentally discovered on the CT scan of 18F-fluorodeoxyglucose (18F-FDG) PET\/CT. We suspected a medullary thyroid carcinoma (MTC) explaining the persistent elevation of CEA. Plasma calcitonin levels were 47 ng\/L (N &lt; 10). Fine needle aspiration cytology found atypia of undetermined significance and the patient was reluctant to undergo surgery without any further exploration. We performed a 18F-fluorodihydroxyphenylalanine (18F-FDOPA) PET\/CT preoperatively which revealed a punctiform focus of the right thyroid lobe corresponding to a pT1aN1aMxR0 medullary thyroid carcinoma, histopathologically confirmed. This case highlights that despite the potential usefulness of 18F-FDG PET\/CT in case of an unknown source of elevated CEA this imaging may be falsely negative as in the case of MTC and should lead to further explorations.<\/jats:p>","DOI":"10.3390\/curroncol28040261","type":"journal-article","created":{"date-parts":[[2021,8,5]],"date-time":"2021-08-05T09:35:32Z","timestamp":1628156132000},"page":"2987-2992","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Carcinoembryonic Antigen Increase in a Patient with Colon Cancer Who Have Achieved Complete Remission and Negative 18F-FDG PET\/CT: Don\u2019t Forget the Thyroid!"],"prefix":"10.3390","volume":"28","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2278-0488","authenticated-orcid":false,"given":"Alexandre","family":"Lugat","sequence":"first","affiliation":[{"name":"Department of Endocrinology, l\u2019Institut du Thorax, CHU de Nantes, H\u00f4pital Nord, 44000 Nantes, France"},{"name":"Center for Research in Cancerology and Immunology Nantes-Angers (CRCINA), University of Nantes, INSERM UMR 1232, 44000 Nantes, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pauline","family":"Hulo","sequence":"additional","affiliation":[{"name":"Center for Research in Cancerology and Immunology Nantes-Angers (CRCINA), University of Nantes, INSERM UMR 1232, 44000 Nantes, France"},{"name":"Thoracic Oncology Unit, CHU de Nantes, H\u00f4pital Nord, 44000 Nantes, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Catherine","family":"Ansquer","sequence":"additional","affiliation":[{"name":"Center for Research in Cancerology and Immunology Nantes-Angers (CRCINA), University of Nantes, INSERM UMR 1232, 44000 Nantes, France"},{"name":"Nuclear Medicine Department, CHU de Nantes, H\u00f4tel-Dieu, 44000 Nantes, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yann","family":"Touchefeu","sequence":"additional","affiliation":[{"name":"Center for Research in Cancerology and Immunology Nantes-Angers (CRCINA), University of Nantes, INSERM UMR 1232, 44000 Nantes, France"},{"name":"Digestive Oncology, Institut des Maladies de l\u2019Appareil Digestif, CHU de Nantes, H\u00f4tel-Dieu, 44000 Nantes, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Eric","family":"Miralli\u00e9","sequence":"additional","affiliation":[{"name":"Department of Digestive and Endocrine Surgery, Institut des Maladies de l\u2019Appareil Digestif, CHU de Nantes, H\u00f4tel-Dieu, 44000 Nantes, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jaafar","family":"Bennouna","sequence":"additional","affiliation":[{"name":"Center for Research in Cancerology and Immunology Nantes-Angers (CRCINA), University of Nantes, INSERM UMR 1232, 44000 Nantes, France"},{"name":"Thoracic Oncology Unit, CHU de Nantes, H\u00f4pital Nord, 44000 Nantes, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Delphine","family":"Drui","sequence":"additional","affiliation":[{"name":"Department of Endocrinology, l\u2019Institut du Thorax, CHU de Nantes, H\u00f4pital Nord, 44000 Nantes, France"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,8,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1016\/0092-8674(89)90970-7","article-title":"Carcinoembryonic Antigen, a Human Tumor Marker, Functions as an Intercellular Adhesion Molecule","volume":"57","author":"Benchimol","year":"1989","journal-title":"Cell"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"263","DOI":"10.1001\/jama.2013.285718","article-title":"FACS Trial Investigators Effect of 3 to 5 Years of Scheduled CEA and CT Follow-up to Detect Recurrence of Colorectal Cancer: The FACS Randomized Clinical Trial","volume":"311","author":"Primrose","year":"2014","journal-title":"JAMA"},{"key":"ref_3","first-page":"CD011134","article-title":"Blood CEA Levels for Detecting Recurrent Colorectal Cancer","volume":"2015","author":"Nicholson","year":"2015","journal-title":"Cochrane Database Syst. 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