Differential Diagnosis for Elevated CEA Level in a Patient with History of Sigmoid Colon Cancer

• Single Most Likely Diagnosis:
  • Recurrence of sigmoid colon cancer: This is the most likely diagnosis given the significant increase in CEA level from a stable range of 3.9-4.2 ng/mL to 11.2 ng/mL. The patient's history of Stage IIB carcinoma of the sigmoid colon and the recent elevation in CEA, a tumor marker commonly associated with colorectal cancer, strongly suggests the possibility of disease recurrence.
• Other Likely Diagnoses:
  • Other malignancies: Although less likely than recurrence of the primary cancer, other types of malignancies could cause an elevation in CEA levels. These might include other gastrointestinal cancers, breast cancer, lung cancer, or medullary thyroid cancer, among others.
  • Benign conditions affecting the liver or pancreas: Certain benign conditions, such as liver disease or pancreatitis, can also lead to elevated CEA levels, although this is less common.
  • Inflammatory bowel disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause an increase in CEA levels due to chronic inflammation in the bowel.
• Do Not Miss Diagnoses:
  • Metastatic disease to the liver or lungs: It is crucial not to miss the possibility of metastatic disease, as it would significantly alter the treatment plan and prognosis. Imaging studies, such as the pending CT abdomen and pelvis, are essential for evaluating this possibility.
  • Second primary malignancy: The possibility of a second primary cancer, either within the colon or in another organ, must be considered and ruled out through appropriate diagnostic tests, including colonoscopy, which has already been done, and other imaging or tumor marker studies as indicated.
• Rare Diagnoses:
  • Other rare tumors: Certain rare tumors, such as carcinoids or islet cell tumors of the pancreas, can also produce elevated CEA levels, although this is uncommon.
  • Familial conditions: Very rare familial conditions could potentially affect CEA levels, but these would be exceptional cases and typically associated with other distinctive clinical features.