 3. Histologically documented adenocarcinoma of the rectum. All other histologic types are excluded. A minimum of 4 biopsies of the rectal primary tumor must be available, with tumor representation 50 in each sample. The samples will be sent to Vall dHebron Institute of Oncology VHIO for molecular determination. The 4 blocks of the 4 biopsies will be sent included in paraffin. 