Multicenter Observational Study Taulí-T1 Classification for the Management of pT1 Rectal Adenocarcinoma

All the slides of each case will be reviewed, selecting the one that contains the most invasive section, and this will be digitized to take measurements in micrometers with greater precision. To measure the degree of infiltration, the measurement of residual healthy submucosa (hrSB) will be used, which is the distance between the point of greatest infiltration and the muscularis propria. The total thickness of the submucosa in the tumor area will also be measured, taking as a reference the muscularis of the mucosa or, in its absence, the surface of the lesion, to calculate the percentage of infiltration of the submucosa. This percentage will be calculated as the inverse percentage of invasion with respect to the hrSB: (total thickness of the submucosa - hrSB / total thickness of the submucosa) x 100. The qualitative categories will be obtained: sm1 (\< 33.3%), sm2 (33.3% - 66.6%) and sm3 (\> 66.6%). Measurements will be also taken in micrometers for the conventional classifications.