Evaluating a Metastatic Carcinoma Using Immunohistochemical Stains for Cytokeratins 7 and 20

Description

If a patient presents with an apparent metastatic adenocarcinoma, then one task for the surgical pathologist may be to suggest some possible sites for the primary tumor. Immunohistochemical staining with cytokeratin (CK) subsets such as cytokeratin 7 and 20 can help narrow the search space.

Questions:

(1) What are the possible sites where the primary tumor could be arising?

(2) If the patient has a history of a previous adenocarcinoma, is this a metastasis or a new primary?

Carcinoma	CK7 + CK20 +	CK7 + CK20 neg	CK7 neg CK20 +	CK7 neg CK20 neg
breast	unlikely	most	unlikely	unlikely
carcinoid	unlikely	unlikely	few	most
colon/rectum	few	few	most	unlikely
endometrioid	few	most	unlikely	few
esophagus, adenocarcinoma	most	unlikely	unlikely	unlikely
gastic	most	few	few	unlikely
hepatocellular	unlikely	unlikely	unlikely	most
lung, adenocarcinoma	unlikely	most	unlikely	unlikely
mesothelioma, epithelial	unlikely	most	unlikely	unlikely
ovarian, mucinous	most	some	few	unlikely
ovarian, serous	most	some	unlikely	unlikely
pancreas/gallbladder	most	unlikely	unlikely	unlikely
prostate	unlikely	unlikely	unlikely	most
renal cell	unlikely	unlikely	unlikely	most
small cell undifferentiated or neuroendocrine	unlikely	unlikely	unlikely	most
squamous	unlikely	unlikely	unlikely	most
thymoma	unlikely	most	unlikely	unlikely
transitional cell	most	unlikely	unlikely	unlikely

Additional immunohistochemical stains may help narrow the search for a primary site.

Carcinoma	Additional Stains Usually Positive	Additional Stains Negative
breast	CEA, ER, GCDFP 15	vimentin
carcinoid	NSE, chromogranin, CEA (few)
colon/rectum	CEA, HCG, CA125 (few)	vimentin
endometrioid	ER, vimetin (many), CA125
esophagus, adenocarcinoma	CEA	vimentin
gastic	CEA, pepsinogen	vimentin
hepatocellular	AFP
lung, adencocarcinoma	CEA, surfactant apoprotein
mesothelioma, epithelial	vimentin, calretinin	CEA, mucin, Leu M1
ovarian, mucinous	CA125, CEA (few)	vimentin
ovarian, serous	CA125	vimentin, CEA
pancreas/gallbladder	CA 19.9, CEA, EMA
prostate	PSA, CEA (few)	vimentin
renal cell	EMA, vimetin, CEA (few)
small cell undifferentiated or neuroendocrine	NSE, chromogranin	vimentin
squamous		CEA, mucin
thymoma	CEA
transitional cell		vimentin

Limitations for immunohistochemical stains:

• definition of positive affects specificity: strong and diffuse vs any

• usually presence or absence of staining is not 100%.

• there are few, true organ specific markers

• some markers such as CEA may be found in tumors from many sites

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Evaluating a Metastatic Carcinoma Using Immunohistochemical Stains for Cytokeratins 7 and 20

Description

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