Lecture on colorectal carcinoma for medical students. Encompasses basic sciences, classifications, staging and principles of management. The author holds a special interest in this topic.

1. Colorectal carcinoma
Chea Chan Hooi
Surgeon
Department of Surgery
Sibu Hospital

2. Content
• Anatomy
• Introduction
• Risk factors
• Pathophysiology
• Clinical features
• Work-up
• Surgical options
• Q&A

3. Anatomy

4. 15cm
11cm
7cm

5. Introduction
• 2nd commonest cancer in Malaysia &
worldwide
• Industrialised countries, lower socio-economic
groups
• Aging population (>80% over 60 y/o)
• 95% sporadic

6. Risk factors
Modifiable
• Diet
• Obesity
• Underlying disorder
– IBDs
– Ureterosigmoidostomy
Non-modifiable
• Genetic predisposition
• Age

7. Pathophysiology
• 3 pathways
– Adenoma-carcinoma sequence
• Loss of heterozygozity
• Usually distal colon, chromosomal aneuploidy
• 5 – 10 years transformation
• 80%
– Microsatellite instability
• Replication error
• Usually right sided cancer, diploid DNA
• 1 – 2 years transformation
• 15%
– PTEN deletion
• 5%
• More aggressive

8. Adenoma-carcinoma sequence

9. Mode of spread
• Direct invasion
– Adjacent organs
• Lymphatic
– Pericolic  perivascular  paraaortic
• Haematogenous
– Portal venous system
• Transperitoneal
– Usually mucinous carcinoma

10. Clinical features
History
• Red flags
– Fresh rectal bleeding
– Mucoid stool
– Tenesmus
– Small caliber stool
– Early morning spurious diarrhoea
– Altered bowel habit
• Loss of appetite, loss of weight
• Abdominal mass
• Abdominal distension
• Metastatic symptoms
• Complications
– Intestinal obstruction 75%
– Peritonitis 20%
– LGIB 5%
– Acute appendicitis
Physical examination
• Anaemia
• Abdominal mass
• DRE
– Distance from AV
– Anal sphincter tone
– Relationship to anorectal ring
– Fixation to rectal/vaginal wall
• Metastatic features
– Virchow’s node
– Pleural effusion
– Lung collapse
– Hepatomegaly
– Ascites
– DVT

11. Work-up
• Confirmatory
– Colonoscopy
• Location of tumour
– Caecum & ascending colon 22%
– Transverse colon 11%
– Descending colon 6%
– Rectosigmoid colon 55%
– Junctions 6%
• Morphology
– Polypoidal, ulcerative, annular
• HPE
• Possibility of obstruction
• Synchronous tumour
• Rigid sigmoidoscopy – only to assess margins from AV
– CT colonography
• As sensitive as colonoscopy
• Unable to obtain tissue for HPE

12. • Histology Types (WHO Classification)
– Adenocarcinoma (95%)
• Epithelial tumour composed of glands
– Mucinous adenocarcinoma
• >50% lesion composed of pools of extracellular mucin.
– Signet ring cell cancer
• >50% tumour cells with prominent intracytoplasmic mucin
– Adenosquamous
• Both squamous & adenocarcinoma features.
– Medullary carcinoma
• Rare variant with vesicular nuclei, prominent infiltration by
intraepithelial lymphocytes
– Undifferentiated cancer
– Lymphoma

13. • Supportive
– Tumour markers
• CEA
• CA 19-9 (only for differentiated adenocarcinoma with
mucinous differentiation)
– FBC
– BUSEC
– AXR
• Only in obstructed patients
• Abrupt cut off of colonic gas

15. • Staging imagings
– Aims:
• Determining the optimal surgical approach
• Assess need for neoadjuvant
• Assess for distant metastasis
– CT scan thorax, abdomen & pelvis
• The main modality for M staging
– MRI pelvis
• Rectal carcinomas
• Assess mesorectal fat for lymphatic infiltration (circumferential resection margin)
– ERUS
• Endoscopic rectal ultrasonography
• Accurate T and N staging
• Disadvantages
– Interobserver variability
– Significant learning curve, not easily available
– Unable to assess posterior CRM
– Not suitable in severely constricting tumour (unable to pass probe) or bulky tumour
– PET scan
• Only for ambiguous CT findings

17. Duke staging

18. TNM staging

19. Surgical options
• Patient presentation
– Elective
– Emergency
• Obstruction
• Perforation
• Bleeding

20. Elective setting
• Formal oncological resection to ensure R0
resection
– En bloc resection of adjacent involved organs
– Longitudinal margins at least 5cm, 2cm distal margin
accepted for rectal carcinoma
– Circumferential margins
• Colon: high ligation of vessels & accompanying lymphatics
• Rectum: total mesorectal excision
• Primary reanastomosis
• ERAS principles

21. Obstructed tumours
• Surgery
– One stage
• Primary resection, on table lavage & primary anastomosis
– Two stage
• Hartmann’s procedure
• Reverse after completed adjuvant therapy
– Three stage
• Defunctioning stoma
• Complete neoadjuvant therapy
• Definitive surgery
• Closure of defunctioning stoma
• Endoscopic stenting
– As a bridge to surgery
• Allows assessment of right colon
• Converts emergency to elective surgery
• Avoid three stage surgery
– As definitive palliative procedure

22. Perforated tumours
• Resuscitation as per Surviving Sepsis
Guidelines
• Surgery
– Damage control principle (two or three stage)
• Staging
• Chemotherapy ± radiotherapy
• Consider definitive surgery if not done yet

23. Bleeding tumours
• Usually stop spontaneously
• Resuscitation
– Stabilised
• Localise bleeding segment
• Staging CT scan as much as possible
• Semi-emergency resection
• Followed by adjuvant therapy
– Unstable
• Emergency resection
• Usually two stage surgery
• Followed by adjuvant therapy