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.