Malignant Colon Cancer

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.