Colon Wall Anatomy
Intraepithelial tumors do not extend beyond the epithelium of the mucosa
Invasive tumors confined to the mucosa
Intramucosal tumors invade the lamina propria but not beyond
Locally invasive tumors
Through the lamina propria into the muscularis mucosa
Through the wall indicates involvement of subserosa
There are many different terms used to describe the involvement or non- involvement by tumor of the layers of the colon wall. Intraepithelial describes a tumor that does not extend beyond the epithelium of the mucosal layer of the wall. Intraepithelial tumors are in situ (non-invasive). Intramucosal tumors invade the mucosa but do not go beyond the lamina propria. These are classified as Tis in AJCC TNM stage, but they are classified as local summary stage. Those tumors that spread through the lamina propria into the muscularis mucosa are locally invasive. When documentation indicates invasion to, into, or through the colon wall without any other descriptors of the wall, the tumor extends into the subserosa. Tumors into the subserosa are locally invasive and defined as AJCC T3 lesions.