Answer and Discussion of Quiz Set: W-001

4. Which of the following combinations of immunohistochemistry would indicate a metastatic colorectal adenocarcinoma?

A. Cytokeratin 7 (-), Cytokeratin 20 (+), thyroid transcription factor 1 (-), villin (+)

B. Cytokeratin 7 (+), Cytokeratin 20 (-), thyroid transcription factor 1 (+), villin (-)

C. Cytokeratin 7 (+), Cytokeratin 20 (+), thyroid transcription factor 1 (-), villin (+)

D. Cytokeratin 7 (+), Cytokeratin 20 (-), synaptophysin (+)

E. Cytokeratin 7 (-), Cytokeratin 20 (-), Cytokerain 5/6 (+)

Answer and Discussion: The answer is (A). These immunohistochemistry results suggest the following tumor of origin:

Immunohistochemical profile	Suggested Tumor of origin
Cytokeratin 7 (-), Cytokeratin 20 (+), thyroid transcription factor 1 (-), villin (+)	Colon and rectum (adenocarcinoma)
Cytokeratin 7 (+), Cytokeratin 20 (-), thyroid transcription factor 1 (+), villin (-)	Lung (adenocarcinoma and small cell carcinoma)
Cytokeratin 7 (+), Cytokeratin 20 (+), thyroid transcription factor 1 (-), villin (+)	Ovary, stomach, pancreas, biliary tract
Cytokeratin 7 (+), Cytokeratin 20 (-), synaptophysin (+)	Small cell carcinoma or neuoendocrine tumor
Cytokeratin 7 (-), Cytokeratin 20 (-), Cytokerain 5/6 (+)	Squamous cell carcinoma from a variety of origins