All posts by peferguson

Organ Systems, Gastrointestinal

Liver – Metastatic Disease

The relative incidence of the origin of tumors in the liver depends primarily upon the underlying condition of the liver itself.  The tumor distribution in a cirrhotic liver is significantly different from a non-cirrhotic liver.  The following are the types and frequencies of tumors for cirrhotic and non-cirrhotic livers.
 
 
Tumor Origin
Cirrhotic Liver
Non-Cirrhotic Liver
Liver
77%
2%
Lung
7%
23%
Colon
4%
13%
Pancreas
2%
18%
Stomach
4%
11%
Breast
–
7%
Other
6%
26%
References
Modern Pathology (2007) 20,S49-S60.
Organ Systems, Gastrointestinal

Gastrointestinal Stromal Tumor (GIST)

GIST Immunohistochemistry Expression
IHC Stain
Percentage
~95%
>95%
80% gastric
50% Sm. Int.
95% Esoph.
95% Rectum
Rare
<1%
~5%
SMA
~35%
Liegl-Atzwanger, et. al. Virchows Arch, Feb. 18, 2010.
Mod Path (2008)21,46-53.
GIST Immunohistochemial Diagnostic Panel
IHC Stain
Comment
>95% sensitivity for GIST
Often + in GIST, less specific
Expressed in Schwannomas, which may have similar morphology to spindle cell GISTs
Expressed in leiomyoma/leiomyosarcoma.  Rare GISTs will show expression
 
It is important to interpret these stains as part of a panel to maximize specificity of diagnosis.
Organ Systems, Gastrointestinal

Colon Adenocarcinoma

Colon adenocarcinomas have a usual and distinctive IHC immunophenotype (CK7-/CK20+), which follows the general trend in the GI tract that CK7 expression changes from positive to negative as one moves proximal to distal, and CK20 expression changes from negative to positive as one moves proximal to distal.
 
Colon Adenocarcinoma
Negative (rare + cases)
Positive (>90%)
Positive
Positive
Usually negative, but up to ~10% may be positive!!!  The CK7/CK20 profile should be reassuring to support a colon primary.
Positive
Positive
CA19-9
+/-
 
It is important to remember that IHC performance is variably dependent on tissue fixation, which can vary widely in colon tissue due to the way cases are often grossed.  Therefore, careful selection is critical in identifying characteristic IHC staining profiles (e.g. CK20 may not stain a colon adenocarcinoma in poorly fixed areas).  Different antibodies have different sensitivities to the amount of fixation.
References
Eisen, Richard N, AIMM Annual Meeting, “Selected Topics in Gastrointestinal, Pancreatic and Hepatic Neoplasia”, presentation, 2010.
 
Diagnostic Immunohistochemistry: Theranostic and Genomic Applications. [edited by] DJ Dabbs. 3rd Edition.  Elsevier, 2010.
Gastrointestinal

Small Intestine Adenocarcinoma

Primary adenocarcinomas of the small intestine are rare but do have some discriminating IHC characteristics.  The IHC profile of non-ampullary adenocarcinomas of the small intestine is different from normal small intestine expression of CK7 and CK20, which is CK20 positive (diffusely) and CK7 negative.
Small Intestine (Non-Ampullary) Adenocarcinoma
Positive
Usually Positive (~60-70%)
Positive (~70%)
Positive (~70%)
Reference
Chen, ZM, et. al. “Alteration of CK7 and CK20 Expression Profile is Uniquely Associated with Tumorigenesis of Primary Adenocarcinoma of the Small Intestine.”Am J Surg Pathol. 2004 Oct;28(10):1352-9.
Organ Systems, Gastrointestinal

Stomach – Adenocarcinoma

Immunohistochemistry
Positive
Positive
Usually Positive (~70%)
Variable (~50%)
It is important to remember that gastric adenocarcinomas may have almost any combination of CK7/CK20 expression!
Usually negative
CK5/6
Usually negative
Variably Positive.  Studies show a wide range of positivity.
+/-
Dim nuclear staining is well-described.
 
HepPar-1, AFP, Chromogranin, and Synaptophysin have been shown to stain some cases.  Clinical and morphologic context must be appreciated at all times and resolved with the IHC findings.  Be careful in performing too many stains, or the “tail may be wagging the dog” so to speak.