What is the definition or description of: colorectal cancer?

Colorectal Cancer: Cancer of the colon (large intestine) or the rectum is most commonly an adenocarcinoma, abnormal cells. Colon cancer is most often treated with surgery first and possible chemotherapy after. Rectal cancer may be treated with radiation & chemotherapy first and surgery later. Treatment of this cancer depends on its stage (tumor depth, lymph nodes, metastatic spread to other sites) & cell type.

Invasion: Colorectal cancer is a term to signify invasion accross a layer of the lining of the colon or rectum. A polyp can show abnormal features up to a point and still not be considered an invasive cancer. Once we use the term colon or rectal cancer, the cells are not only atypical, they have shown invasion.