Tubular Adenoma : High-grade Dysplasia
Features of high-grade dysplasia in tubular adenoma are: nuclear enlargement, pleomorphism, nuclear hyperchromasia, loss of polarity, enlarged nucleoli, and further loss of goblet cell mucin. There is considerable hypercellularity, glandular crowding and increased mitotic activity. Atypical mitoses may be present. Carcinoma-in-situ: The features mentioned above are further advanced. Cellular proliferation and loss of polarity creates glands within glands with a cribriform appearance. The proliferation is confined to the crypts leaving the basement membrane intact surrounding the glands. Carcinoma-in-situ or intraepithelial carcinoma simply reflect the extreme end of high-grade dysplasia spectrum. They are included in high-grade dysplasia category to avoid using the term “carcinoma” since these lesions can be managed endoscopically. The frequency of dysplasia in adenomatous polyps is as follows: 1) Tubular adenomas: low-grade 90-95%; high-grade 5-10%. 2) Villous adenomas: low-grade 70-80%; high-grade 20-30%.