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Tumours of Large Intestine
Dr.C.P.Ganesh babu, M.S.,
Anatomic Location of CRC• Cecum 14 %• Ascending colon 10 %• Transverse colon12 %• Descending colon 7 %• Sigmoid colon 25 %• Rectosigmoid junct.9 %• Rectum 23 %
Symptoms associated with CRC
Colon cancers result from a series of pathologic changes that transform normal epithelium into invasive carcinoma. Specific genetic events, shown by vertical arrows, accompany this multistep process.
WHO Classification of CRC• Adenocarcinoma in situ / severe dysplasia• Adenocarcinoma• Mucinous (colloid) adenocarcinoma (>50%
mucinous)• Signet ring cell carcinoma (>50% signet ring
cells)• Squamous cell (epidermoid) carcinoma• Adenosquamous carcinoma• Small-cell (oat cell) carcinoma• Medullary carcinoma• Undifferentiated Carcinoma
Risk factors for CRC
• Age• Adenomas, Polyps• Sedentary lifestyle, Diet, Obesity• Family History of CRC• Inflammatory Bowel Disease (IBD)• Hereditary Syndromes (familial adenomatous
polyposis (FAP))
Dietary factors implicated in colorectal carcinogenesis
Increased risk
• consumption of red meat
• animal and saturated fat
• refined carbohydrates
• alcohol
Dietary factors implicated in colorectal carcinogenesis
Decreased risk
• dietary fiber
• vegetables
• fruits
• antioxidant vitamins
• calcium
• folate (B Vitamin)
Specimen containing an invasive colorectal carcinoma and two adenomatous polyps.
Multiple adenomatous polyps of the cecum are seen here in a case of familial polyposis.
Familial polyposis in which mucosal surface of the colon is a carpet of small adenomatous polyps. Even though they are small , there is a 100% risk over time for development of adenocarcinoma, for which total colectomy is recommended
Adenocarcinoma of the cecum demonstrates an exophytic growth pattern.
Staging of CRC• TNM system
• Primary tumor (T)
• Regional lymph nodes (N)
• Distant metastasis (M)
*Note: Tis includes cancer cells confined within the glandular basement membrane (intraepithelial) or lamina propria (intramucosal) with no extension through the muscularis mucosae into the submucosa.
**Note: Direct invasion in T4 includes invasion of other segments of the colorectum by way of the serosa; for example, invasion of the sigmoid colon by a carcinoma of the cecum.
Dukes staging system
A Mucosa 80%B Into or through M. propria 50%C1 Into M. propria, + LN ! 40%C2 Through M. propria, + LN! 12%D distant metastatic spread <5%
Sites of metastasis
Liver
Lung
Brain
Bone
Via blood
Lymph nodes
Abdominal wall
Nerves
Vessels
Via lymphatics Per continuitatem
Diagnosis
• Colonoscopy is the preferred diagnostic test for colorectal cancer
• Barium enema and fl exible sigmoidoscopy.• Biopsy of suspicious lesions is required to establish
a diagnosis.• Tumor markers such as carcinoembryonic antigen
(cea) or carbohydrate antigen (ca).• Radiologic studies are used to evaluate the extent of
local disease and to screen for metastatic disease.
Therapy
• Surgical resection the only curative treatment
• Likelihood of cure is greater when disease is detected at an early stage
• Early detection and screening is of pivotal importance