A 65 year-old man with no past medical history presents for his annual check-up. He notes some increased dyspnea on exertion along with an overall lethargic feeling for the past few months. Physical exam is normal with the exception of a heme-occult positive stool test, and he is subsequently found to have elevated liver function tests. Which of the following is true?
A peripheral blood smear will show microcytic erythrocytes
A CEA level will be at least twice the upper limit of normal
A peripheral blood smear would show polymorphonuclear cells with more than five lobes of the nucleus
A biopsy of the primary lesion will show signet-ring cells
A CEA level will be undetectable
Correct answer
A peripheral blood smear will show microcytic erythrocytes
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correct answer: A
The answer is A. The patient most likely has adenocarcinoma of the colon until proven otherwise. The heme-occult stool test has
95% sensitivity for this disease and colon cancer also can lead to iron-deficiency anemia. Iron-deficiency anemia manifests as microcytic hypochromic erythrocytes on a peripheral blood smear.
Choice B is incorrect; while a CEA level may be monitored prior to resection and afterwards to detect recurrence or liver metastases, it may not be elevated in many patients with colorectal cancer. CEA levels should not be used to diagnose or screen for colorectal cancer.
Choice C is incorrect; hypersegmented PMNs are the first indication of B12 or folate deficiency anemias.
Choice D is incorrect; a biopsy of adenocarcinoma of the colon will most likely not show signet rings. This pathology finding is more likely to be associated with gastric cancer although it is sometimes found in colon cancer.
Choice E is incorrect; CEA levels are rarely undetectable. Also see explanation for choice B above.