Download Cancer colon

Cancer colon
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• The peak incidence for colorectal carcinoma is
between ages 50 and 80. Fewer than 20% of cases
occur before age 50.
• When colorectal carcinoma is found in a young
person, pre-existing ulcerative colitis or one of the
polyposis syndromes must be suspected.
• Male-to-female ratio is 1.2:1.
• Colorectal carcinoma has a worldwide distribution,
with the highest death rates in the United States.
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* Risk factors for cancer colon:
1. Genetic predisposition.
2. Dietary factors.
3. Precancerous lesions:
– Colonic adenoma.
– Hereditary familial polyposis coli.
– Ulcerative colitis.
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• The dietary factors receiving the most attention as
predisposing to a higher incidence of cancer colon are:
A diet with high calories and low fibers is risky….
• Mechanism:
1. Reduced fiber content leads to decreased stool bulk, increased
fecal transit time in the bowel, and an altered bacterial flora of
the intestine. Potentially toxic oxidative byproducts of
carbohydrate degradation by bacteria are therefore present in
higher concentrations in the stools and are held in contact with
the colonic mucosa for longer periods of time.
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Diet and cancer colon
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2. High content of refined carbohydrates which contain
less of vitamins A, C, and E, which act as oxygen-radical
scavengers.
3. Excess intake of red meat: High cholesterol intake in
red meat enhances the synthesis of bile acids by the liver,
which in turn may be converted into potential
carcinogens by intestinal bacteria.
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* Morphology:
- The distribution of the cancers in the colo-rectum is
as follows:
• Rectosigmoid colon 55%.
• Cecum/ascending colon 22%
• Transverse colon 11%.
• Descending colon 6%.
• Other sites 6%.
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• Tumors in the proximal colon tend to grow as
polypoid, exophytic masses. Obstruction is
uncommon.
• While carcinomas in the distal colon tend to be
ulcerative forming malignant ulcer or tend to be
infiltrative forming annular, encircling lesions that
produce malignant constrictions of the bowel.
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Ulcerative colonic carcinoma
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Polypoid colonic carcinoma
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Infiltrative colonic carcinoma
(annular stricture)
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* Microscopically; cancer colon is
adenocarcinoma consists of malignant acini
separated by fibrovascular connective tissue
stroma.
• The tumor infiltrates the wall down to the
serosa according to the tumor stage.
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Adenocarcinoma
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Colonic adenocarcinoma: malignant acini
infiltrates the wall.
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* Clinical Features:
• Colorectal cancers remain asymptomatic for years.
• Ceacal and right colonic cancers cause fatigue,
weakness, and iron-deficiency anemia. These bulky
lesions bleed readily and may be discovered at an
early stage.
• Left-sided cancers cause occult bleeding, changes
in bowel habit, or crampy left lower quadrant
discomfort.
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• All colorectal tumors spread by direct extension
into adjacent structures and by metastasis
through the lymphatics and blood vessels.
• In order of preference, the favored sites of
metastatic spread are the regional lymph
nodes, liver, lungs, and bones.
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TNM Staging of cancer colon
Tis
Carcinoma in situ
T1
Tumor invades submucosa
T2
Extending to the muscularis propria
T3
Extending to subserosa
T4
Tumor directly invades adjacent organs
N0
No regional lymph node metastasis
N1
Metastasis in 1 to 3 lymph nodes
N2
Metastasis in 4 or more lymph nodes
M0
No distant metastasis
M1
Distant metastasis
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* Complications of cancer colon:
1. Intestinal obstruction.
2. Bleeding per rectum and anemia.
3. Intestinal perforations.
4. Fistula formation.
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Radiographic features
1. Barium enema:
• Will reflect gross appearance of the tumor;
a. Filling defect sign in polypoid masses.
b. Apple core sign in circumferential lesions.
• Fistulas to bladder, vagina or bowel may also be
demonstrated.
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Apple core sign
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2. CT and MRI:
• Are used for staging of colorectal carcinoma
and able to asses draining lymph nodes and
metastases.
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* Treatment and prognosis:
• Treatment involves resection in almost all
cases. Adjuvant chemotherapy is reserved
for stage III disease.
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THANKS
References:
Robbins and Cotran’s: Pathologic Basis of Disease. Seventh edition.
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