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