cancer colon 1. the peak incidence for colorectal carcinoma is between ages 60 and 79. fewer than...
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Cancer colon
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• The peak incidence for colorectal carcinoma is
between ages 60 and 79. 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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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 colorectum
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 colonTis Carcinoma in situ
T1 Tumor invades submucosa
T2 Extending into the muscularis propria
T3 Penetrating through the muscularis propria into subserosa
T4 Tumor directly invades other organs or structures
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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THANKS
References:Robbins and Cotran’s: Pathologic Basis of Disease. Seventh edition.