Colorectal carcinoma invading the submucosa but not the muscular layer (pT1, early invasive cancer) represents the earliest form of clinically relevant colorectal cancer in most patients.

The following histological features predict the risk of metastasis and the different clinical outcomes: grade of differentiation of carcinoma, lymphovascular invasion, state of the resection margin. Microstaging of invasive cancer, namely the width and the depth of submucosal invasion, together with tumor budding at the advancing edge allow the metastatic risk to be further stratified in minimal, low, and high.

Cancerised adenomas (pT1 cancers) represent the earliest form of clinically relevant colorectal cancer in most patients. Invasion of the submucosa opens the way to metastasis and the choice between endoscopic surveillance and major surgery turns on their metastatic potential.