Adenocarcinoma of the colon
Risk factors
- Low-fiber diet
- Diet low in fruits and vegetables
- High red meat and animal fat consumption
- Adenomatous polyps
- Hereditary polyposis syndromes
- Lynch syndrome
- Ulcerative colitis
Genetics
- Multiple mutations are involved
- APC gene
- K-ras oncogene
- p53 gene
Pathology
Microscopically:
It is columnar cell carcinoma originating in the colonic epithelium.
Macroscopically: 4 forms
Annular- may give rise to obstructive symptoms
Tubular- presents with bleeding
Ulcer-presents with bleeding
Cauliflower- least malignant-presents with bleeding
Tumors are more common in the left colon and rectum.
Spread
Direct Spread:
Locally it can invade the bladder, obstruct ureter and may cause hydronephrosis.
Can perforate and cause peritonitis/pericolic abscess/ faecal fistula.
Lymphatic spread:
Growth through lymphatics spreads to pericolic, epicolic, intermediate and principal group of lymph nodes.
Bloodstream spread: To the liver via portal system
Staging colon cancer: Modified Dukes' Staging
Stage
A
B1
B2
C1
C2
D
Extent of Disease
Limited to the mucosa and submucosa
Invasion into but not through the muscularis propria
Invasion through the muscularis propria
Positive lymph nodes; invasion into but not through the muscularis propria
Positive lymph nodes; invasion through the muscularis propria
Distant metastasis
Clinical features
Age: common in patients over 50 yrs of age.
Carcinoma of the left side of the colon:
Most tumors occur in this site and are of stenosing variety.
Main sympton- increasing intestinal obstruction.
Pain
Pain is referred to suprapubic area. Pt. have episodic colicky pain. Constant pain suggests advanced tumors.
Altered bowel habit:
The episodes of constipation may be followed by attacks of diarrhoea.
Palpable lump
Distension: Lower abdominal distension.
- Carcinoma of sigmoid
Same features as above with there variations:
Pain
Pain
Tenesmus
Low tumors give rise to a feeling of the need for evacuation, which result in tenesmus accompanied by the passage of mucus (esp. in the early morning)
Bladder symptoms
Carcinoma of transverse colon:
May be mistaken for a carcinoma of the stomach because of the position of the tumor together with anemia and lassitude.
Carcinoma of the caecum and ascending colon:
Anemia
Presence of mass in the right iliac fossa.
Can present with obstruction
Metastatic disease:
Pt. may also present for the first time with liver metastases and an enlarged liver, ascites,
Rarely pt. may also present metastases to the lung, skin, bone and brain.
Right V/S left sided cancer
Right-Sided Cancer
Gross
Polypoid mass
Barium studies
Polypoid mass
Presentation
Bleeding
Occult blood in stool
Iron deficiency anemia
Left-Sided Cancer
Gross
Circumferential growth producing a "napkinring“ Configuration
Barium studies
"Apple core" lesion
Presentation
Change in bowel habits
Constipation or diarrhea
Reduced caliber stools
Obstruction
Investigations
Sigmoidoscopy
It is a part of the routine investigation of patients passing blood and mucus if it limited to rectum.
Colonoscopy
Used in pts. With presenting symptom of bleeding, those with polyps and in those with radiological doubt.
Radiology
Double-contrast barium enema is used
It shows irregular filling defect and apple core lesion( in lt. sided Ca)
Ix of choice in pt. with a predominant change in bowel habit as a presenting symptom.
USG
For screening of liver metastases
CT
to determine the local invasion in case of large palpable abdominal mass.
Treatment
For right sided growth
Right radical hemicolectomy with ileo transverse anastomosis is done.
Structures removed are-terminal 30cm of ileum, caecum, appendix, ascending colon, 1/3 transverse colon and lymph nodes (epicolic, paracolic, intermediate)
In inoperable right sided growth, ileo-transverse anastomosis is done as a bypass procedure.
For left sided growth
Left radical hemicolectomy is done.
Structures removed are- left ½ of tansverse colon and descending colon is removed along with lymph nodes.
Left sided stenosing type of growth can present with acute intestinal obstruction, in which case initially colostomy is done. Later after 3-6 wks, following proper preparation, required procedure is done, followed by closure of colostomy after 8 wks.
In solitary liver secondary
Segmental hepatic resection is done.
In case of multiple secondaries confined to one lobe of the liver, hemihepatectomy can be done.
Adjuvant therapy
Chemotherapy using 5-FU and cyclophosphamide.
Regimes-Levamisole and 5-FU or Leucoverin and 5-FU
Indications-Positive nodes, T4 lesion, Venous spread, Signet cell type, Poorly differentiated, Changes in CEA level.
Hepatic metastases
Hepatic resection after recovery from colonicresection.
Irresectable symptomatic hepatic metastases may be treated with cytotoxic drugs or ablaative treatments.
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