Most TSAs are villiform or pedunculated (as seen here), but occasionally, may be sessile.
Note the ectopic crypts which don't connect to the muscularis mucosa. There is a very pink look to the epithelium.
The epithelial cells are hypereosinophilic, columnar and rather uniform.
The nuclei are elongated and pseudostratified. There is mild dysplasia.
A closer look at the pseudostratified elongated nuclei.
This is a different case and shows prominent serrations. Like conventional adenomas, TSAs have uniform, overt cytological dysplasia (enlargement, variation of nuclear size and shape, nuclear hyperchromasia.
Aberrant crypts can be seen nicely in this image, along with promient serrations.
The cells are nicely pink throughout.
Traditional serrated adenoma (TSA) is broadly defined as a polyp that shows a prominent serrated architectural growth pattern and evidence of dysplasia. They are uncommon (1-2% of colon polyps). The pathogenesis of TSAs is not fully understood and they are treated similar to conventional adenomas.
TSAs are most common in females and occur almost exclusively in the left colon (sigmoid, rectum). This is in contrast to sessile serrated adenomas, which generally arise in the right colon.
Microscopically, TSAs are characterized by epithelium with confluent pink eosinophilic cytoplasm, prominent crypt serration, and dyplasia (nuclear atypia and nuclear stratification). SSAs also display hyperplastic serrated growth, but exhibit little to no dysplasia. Ectopic crypt formation (ECF) defined by the presence of ectopic crypts with their bases not seated adjacent to the muscularis mucosae, is unique to this lesion.
Text is supplied by Dr. Kate Sciandra, Dept of Pathology, VAMC Albuquerque New Mexico.