Hyperplastic Polyp / Mucosal Hyperplasia of the Appendix

Definition

Serrated mucosal proliferations in the appendix lacking both architectural and cytological dysplasia

Mucosal hyperplasia, hyperplastic polyp and sessile serrated polyp have quite similar appearances in the appendix
- Architectural distortion due to obstructive changes may make the distinctions difficult
- Criteria for their distinction have not been tested for reproducibility in the appendix
- Architectural criteria for separation of sessile serrated polyp from hyperplastic lesions are based on those used in the colorectum
Appearance is similar to hyperplastic polyp of the colorectum
- Upper (luminal) portion of polyp has a “saw tooth” appearance
- Nuclei are small, regular, round and basal
  - Best evaluated on or near the luminal surface
- Bases of crypts show proliferative changes
It is not clear that hyperplastic polyps and mucosal hyperplasia can or need to be separated in the appendix
- Polypoid vs. sessile distinction has been proposed
  - This is not reliably made in the appendix
  - Both are common incidental lesions
  - Both are uncommonly associated with appendiceal dilation
  - Neither has been shown to be a precursor of carcinoma or be associated with pseudomyxoma peritonei
The entire appendix should be examined microscopically

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342