Introduction: Carcinoembryonic antigen (CEA) is a commonly used tumor marker, and its value in colon cancer is well established. However it is overexpressed in many different tumors. Here we report a case of colorectal cancer with high postoperative CEA levels that were associated with medullary thyroid carcinoma.
Case: A 60-year old man was operated for colon cancer. Postoperative CEA level was 107.6 ng/mL, while preoperative CEA level was unknown. For the detection of distant metastasis or local recurrence, we performed 18-flouro deoxyglycose (FDG) positron emission tomography (PET) and computed tomography (CT). We observed an increased FDG accumulation in the right lobe of the thyroid. The patient had cystic and non-metabolic lesions in the liver, and started a treatment with FOLFOX regimen. After 3 months of chemotherapy CEA was still as high as 146 ng/mL. There was no pathologic FDG uptake other than the thyroid nodule in PET-CT. Fine needle aspiration of the thyroid nodule revealed a follicular neoplasia. The patient underwent total thyroidectomy and histopathology revealed a medullary thyroid carcinoma. Postoperative CEA levels then lowered to normal ranges.
Conclusion: The case we here report was a stage III colorectal cancer with high CEA levels. Our focus on searching a residual/metastatic disease made us blind to other possible explanations; in fact, none of us noticed the thyroid nodule. This case reminds us not to forget that high CEA levels can be associated with conditions other than colon cancer, such as thyroid medullary carcinoma.