A case of false-positive tumor markers in a colon cancer patient with diabetes mellitus

Abstract

A 80-year-old woman was diagnosed as having sigmoid colon cancer. She underwent an operation. Eight months after the operation, her general condition worsened. CT scan and colonoscopy done 1 year postoperatively revealed no metastasis or recurrence. However, tumor marker (CEA and CA19-9) levels were high. At about the same time, the patient developed diabetes mellitus (DM) for which she was treated. With DM treatment, the tumor marker levels returned to normal. It was suspected that the false-positive tumor marker levels were due to the presence of untreated DM.