Rectal Cancer

Some good links:
Cancer Incidence Projections (Australian Government)


Incidence, age of onset, gender, geography

Aetiology and Pathogenesis

Individual causative factors

Natural History

Precursor lesions
Modes of spread

Clinical Presentation

Blood Findings
Imaging Findings

Tumour/Normal Tissue Features

Laboratory Diagnosis
- macroscopic, microscopic, architecture, grading, growth patterns, immunohistochemistry, molecular techniques, serum markers


The TNM staging system is recommended by most organisations. Duke's staging, which applies to malignancies of the large bowel, is commonly quoted - particularly in older studies and by surgeons.

TNM Staging

For the rectum, clinical and pathological stages are identical.

Tumour Stage

The depth of invasion through the muscular wall of the rectum is an important guide.

  • TX - Primary tumour unable to be assessed
  • T0 - No evidence of primary tumour
  • Tis - Carcinoma in situ
    • This includes invasion through the basement membrane, into the lamina propria; but not into the muscularis mucosae which separates the mucosa from the submucosa
  • T1 - Invasion of submucosa
  • T2 - Invasion into the muscularis propria
  • T3 - Invasion through muscularis propria into the surrounding fat
  • T4a - Invasion to the surface of the visceral peritoneum
  • T4b - Invasion of adjacent organs

Nodal Stage

The regional nodes of the rectum include perirectal, sigmoid mesenteric, inferior mesenteric, superior, middle and inferior rectal groups, and the internal iliac nodes.

  • NX - Unable to be assessed
  • N0 - No regional lymph node metastases
  • N1 - 1-3 regional lymph nodes involved
    • N1a - 1 regional node
    • N1b - 2-3 regional nodes
    • N1c - Perirectal nodes with no regional node involvement
  • N2 - 4 or more regional lymph nodes involved
    • N2a - 4-6 regional nodes
    • N2b - > 6 regional nodes

Distant Metastases

Due to the increased potential for cure when metastases are localised to a single site, the M stage for rectal cancer is divided into M1a and M1b.

  • MX - Unable to be assessed
  • M0 - No distant metastases
  • M1a - Distant metastatic disease to a single organ or site, except the peritoneum
  • M1b - Distant metastatic disease to more than one organ or site, or to the peritoneum

Overall Stage

  • Stage 0 is in situ disease
  • Stage I is T1 or T2, with no nodal metastases. This correlates with Dukes A stage.
  • Stage II is T3 (IIA), T4a (IIB) or T4b (IIC) with no nodal metastases, correlating with Dukes B stage.
  • Stage III denotes the presence of nodal metastases. It correlates with Dukes C stage.
    • Stage IIIA: T1/2 and N1; or T1 with N2a
    • Stage IIIB: T1-2 with N2b, T2-3 with N2a, and T3-4a with N1 disease
    • Stage IIIC: T4a with N2a disease, T3-T4a with N2b disease, or T4b with any nodal involvement
  • Stage IVA is the presence of M1a metastatic disease; Stage IVB is the presence of M1b metastatic disease. This is equivalent to Dukes D stage.

Dukes Staging

The Dukes staging system was proposed for rectal cancer in 1932 by a pathologist, Dr. Dukes, and was commonly used until recently when TNM staging became the staging system of choice.

  • Dukes A was disease that did not penetrate the muscular wall of the colon/rectum
  • Dukes B was disease that did penetrate the wall but did not have any lymph node metastases
  • Dukes C was disease that had nodal involvement but no distant metastases

Note: There was no stage for distant metastatic disease in the original Dukes staging. This was added later as 'Dukes D'.
The Dukes staging system was adapted for the colon in 1953 by Astler and Collins.

MAC Staging

The Modified Astler Coller staging system was developed using the Dukes system as a base.

  • MAC A is 'in situ' disease that does not invade through the muscularis mucosae
  • MAC B1 is disease that invades into but not through the muscularis propria
  • MAC B2 is disease that invades through the muscularis propria
  • MAC C1 and C2 is based on B1/B2 but with nodal involvement
  • MAC D is distant metastatic disease