Diagnosis

History

Presenting Complaint

Patients often present with non-specific symptoms, related to anaemia, obstruction or advanced disease. These can include fatigue, bloating, abdominal discomfort, rectal bleeding, or weight loss.

Past History

Patients with inflammatory bowel disease are at 3 (Crohn's) to 4 (Ulcerative Colitis) times the risk of developing colorectal cancers. Patients with familial conditions (familial adenomatous polyposis or Lynch syndrome) may have a previous history of other malignancies or multiple polyps removed.

Family History

Family history is important in detecting cases of familial colon cancer; some patients may be the 'index case' when they present for their family and a negative family history does not exclude a familial condition.

Social History

Some lifestyle factors are associated with an increased risk of colon cancer, such as low fibre diet and high levels refined carbohydrates.

Examination

Examination should be directed to evaluate liver involvement or distant metastases. A mass is usually not palpable.

Bloods

General bloods should include:

  • FBE - evaluate extent of anaemia
  • LFT - in case of liver involvement
  • CEA - to determine whether this is elevated in the patient's tumour and may allow following of the value post-therapy

Imaging

CT scan of the chest, abdomen and pelvis allows locoregional and distant staging of colon cancer. PET scanning is not funded in Australia. MRI is not usually indicated (unlike for rectal cancer).

Histological Diagnosis

Colonoscopy is usually performed for evaluation of the patient's symptoms or if there is a suspicious lesion seen on CT. Biopsy from this procedure usually confirms the diagnosis.

Staging

Colon cancer is currently staged using the TNM system. Older staging system include the Dukes stage and MAC stage.

T Stage

  • Tis: Confined to mucosa or lamina propria
  • T1: Invades submucosa
  • T2: Invades muscularis propria
  • T3: Invades outside muscularis propria into adventitial fat
  • T4a: Invades through to surface of visceral peritoneum
  • T4b: Invades adjacent organs or structures (eg. psoas muscle)

N Stage

  • N1a: Metastasis to single regional node
  • N1b: Metastasis to 2-3 regional nodes
  • N1c: Non-lymph node metastases to subserosal, mesenteric or pericolic tissue with no lymph node deposits
  • N2a: Metastasis to 4-6 regional nodes
  • N2b: Metastasis to > 6 regional nodes

M Stage

  • M1a: Metastasis to single distant site (eg. liver, non regional node)
  • M1b: Metastasis to more than one organ or site, or peritoneal metastases

Dukes Staging

The Dukes staging system is much older and was developed in the first part of the 20th century.

  • Dukes A: No penetration outside muscularis propria
  • Dukes B: Penetration beyond muscularis propria but no lymph node metastases
  • Dukes C: Regional node metastases

"Dukes D" was not used in the original staging system but colloquially refers to metastatic disease.

Modified Astler-Coller Staging (MAC)

This was a re-imagining of the Dukes staging system developed in 1954. It used similar notation to the Dukes staging system but added numerals to denote more advanced lesions within a particular category.

  • MAC A: Confined to submucosa
  • MAC B1: No penetration beyond muscularis propria
  • MAC B2: Invasion into pericolic fat or penetration through visceral peritoneum
  • MAC B3: Invasion of adjacent organs
  • MAC C1: B1 disease with regional lymphadenopathy
  • MAC C2: B2 disease with regional lymphadenopathy
  • MAC C3: B3 disease with regional lymphadenopathy

Final TNM / Dukes / MAC Stage

The Dukes and MAC stage correspond somewhat to modern TNM staging and are listed for comparison here (based on AJCC TNM Staging 7th Edition).

TNM Stage T N M Dukes MAC
I T1-2 N0 M0 A A - B1
IIA T3 N0 M0 B B2
IIB T4a N0 M0 B B2
IIC T4b N0 M0 B B3
IIIA T1-2
T1		 N1
N2a		 M0 C C1
IIIB T3-4a
T2-3
T1		 N1
N2a
N2b		 M0 C C2
C1-2
C1
IIIC T4a
T3-4a
T4b		 N2a
N2b
NAny		 M0 C C2
C2
C3
IVA Tany Nany M1a X X
IVB Tany Nany M1b X X

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