Colorectal tumours

Colorectal tumours are very common. They are the bread and butter of GI pathology. Non-tumour colon is dealt with in the colon article.

An introduction to gastrointestinal pathology is in the gastrointestinal pathology article.

Classification

• Colon & rectum, most common --by far-- is adenocarcinoma.

Other tumours - many (incomplete list):

• Mucinous carcinoma.
• Adenosquamous carcinoma.
• Signet-ring carcinoma.
• Squamous carcinoma.
• Neuroendocrine neoplasms (carcinoid tumours).
• Lipoma.
• Leiomyoma.
• Gastrointestinal stromal tumour (GIST) - dealt with in a separate article.
• Angiosarcoma.
• Lymphoma (Non-Hodgkin's lymphoma).

Grading

• "Adenocarcinoma in situ" and "high-grade dysplasia" is used interchangeably by many in the colon and rectum.
  • Splitting hairs - adenocarcinoma in situ is invasion into the lamina propria, high-grade dysplasia does not have lamina propria invasion. Ergo, the difference (in my opinion) amounts to seeing a desmoplastic stroma (adenocarcinoma) or not seeing one (dysplasia).

Grading of tumours:

• Tis - in situ (intramucosal),
• T1 - into submucosa (through mucularis mucosae),
  • this is different than elsewhere,
• T2 - into muscularis propria,
• T3 - into fat beyond musclaris propria,
• T4 - into something else.

Nodes:

• N0 - no positive nodes.
• N1 - 1-3 positive nodes.
• N2 - 4+ positive nodes.

Staging of colorectal cancer

Simple version

Tumour/node grade for stage:

• Stage I - T1 or T2 N0 M0.
• Stage II - T3 or T4 N0 M0.
• Stage III - Tx N1 or N2 M0.
• Stage IV - Tx Nx M1.

Complex version

Detailed tumour/node grade for stage:

• Stage I - T1 or T2.
• Stage IIA - T3.
• Stage IIB - T4.
• Stage IIIA - T1 N1 or T2 N1.
• Stage IIIB - T3 N1 or T4 N1.
• Stage IIIC - Tx N2.
• Stage IV - Tx Nx M1.

See also

• Colon.
• Gastrointestinal pathology.