EOD Primary Tumor

For Colorectal tumors, extent of the tumor is based on how far the tumor has gone through the colon wall and/or into adjacent organs

  1. In situ, confined to the epithelial layer, basement membrane or the lamina propria
    • Note: In prior versions of AJCC, the lamina propria was assigned a T1. This was moved to a Tis. Since Summary Stage does not change, invasion of the lamina propria continues to be a localized tumor and has its own code in EOD Primary Tumor. Behavior must be 3; however, Derived EOD T will be Tis.
  2. Submucosal invasion
  3. Muscularis propria invasion
  4. Invasion of tumor through the muscularis propria and into pericolorectal tissue (see note below)
    • Extension through the wall
    • Subserosal tissue
  5. Invasion of the serosa/visceral peritoneum/mesothelium
  6. Invasion of perivesical fat
  7. Direct invasion of adjacent organs

Invasion of pericolonic/pericolorectal tissue

Note: This section ONLY applies to tumors that have invaded through the muscularis propria and into pericolorectal tissue (does not include tumors that have invaded the mesothelium, serosa, tunica serosa, or adjacent structures)

When the pathology report states “invasion of pericolonic or pericolorectal tissue”

  • Determine first if you have a peritonealized subsite.
  • Completely peritonealized subsites include Cecum, Transverse colon, Sigmoid Colon, and Rectosigmoid colon.
  • Subsites with segmental surfaces that are peritonealized include the anterior and lateral surfaces of the ascending colon, descending colon, hepatic flexure, splenic flexure, upper third of rectum, middle third of rectum.
  • If unable to determine if subsite or segmental surface is peritonealized, default to not peritonealized.
  • See EOD Primary Tumor for further instructions on how to code.

Updated: June 24, 2025