Category Archives: Organ Systems

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.
Organ Systems, Gastrointestinal

Esophageal Squamous Cell Carcinoma

Immunohistochemistry
Positive
Positive
34BE12
Positive
Positive
Usually negative (<20% +)
Negative
 
There is evidence that CD5 may be used to differentiate thymic carcinomas (+) from esophageal SCC (-), but this is dependent upon the antibody clone used and the antigen retrieval method.  Otherwise, both may stain.  Use of CD5 in this setting would not be advised unless one’s laboratory has specifically validated the antibody for this differential diagnosis.
Organ Systems, Gastrointestinal

Barrett’s Esophagus

Immunohistochemsitry
  • CDX-2, Villin, and/or HepPar-1 may be early markers of intestinal metaplasia before goblet cells are readily identifiable.  These markers may be helpful to identify intestinal metaplasia in the setting of an endoscopic exam c/w Barrett’s esophagus, but the biopsy fails to demonstrate goblet cells.
  • p53 usually shows strong diffuse positivity in high-grade dysplasia in Barrett’s esophagus.  Weak and focal positivity may be seen in biopsies ranging from reactive changes to low-grade dysplasia.
Organ Systems, Gastrointestinal

Gastrointestinal Tract

General Comments (IHC)
As a general principle, tumors of the GI tract will have an IHC profile similar to the associated normal mucosal immunophenotype.  The following are some general principles:
  • CK20 is minimally expressed proximally, and maximally expressed distally
  • CK7 is maximally expressed proximally, and minimally expressed distally
  • Villin is expressed with microvillus brush border (excludes gastric glandular and foveolar⁃mucosa)
  • CK19 and CA19-9 are more commonly expressed in proximal and pancreatobiliary tumors
  • CDX-2 expression diminishes from distal to proximal.
Mucin-related antigens (MUC1, MUC2, MUC4, etc.) are generally organ selective, but show aberrant expression in GI tumors, and is therefore not particularly helpful diagnostically.
Organ Systems

Mediastinum

The mediastinum is a location, which may have a broad diversity of neoplastic processes.  There are several common categories that are important to differentiate from each other.  The following list are some of the more common entities encountered in the mediastinum.  This is certainly not a complete list.
 
Organ Systems, Gynecological, Cervix

Cervix – HGSIL

High-Grade Squamous Intraepithelial Lesions
Strong diffuse cytoplasmic and nuclear positivity in the vast majority of cells.
Markedly increased proliferation indue with positive staining occurring in the upper half of the epithelium (occasionally extending to the epithelial surface.
References

Matt Quick, MD (personal communication)