What are the histologic features of conventional adenomas?
Tubular adenomas have a tubular architecture with the surface epithelium showing low-grade dysplasia that extends downward in the base. These can show focal areas of high-grade dysplasia with architectural complexity and marked cytologic atypia. Focal high-grade dysplasia does not have a metastatic potential. The tubulovillous adenomas show a combination of tubular and villous architecture (villous component greater than 25%).
Villous adenoma displays a predominant villous architecture (greater than 75%) and has a greater propensity for malignant transformation.
All of these can have focal areas of pseudoinvasion that should not be interpreted as intramucosal carcinoma. The conventional adenomas show KRAS mutations ( BRAF negative).