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Colon tumor

Carcinoma

General of colon


Reviewers: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 12 January 2012, last major update September 2011
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● 98% of colonic cancers are adenocarcinomas
● #2 cause of cancer deaths in US after lung cancer with 185,000 new cases and 55,000 deaths/year
● Affects 5% of US population during their lifetime
● Most common GI tumor in US; less common in Africa, Asia and parts of South America
● Peak age 60-79 years; < 20% before age 50
Risk factors: older age, obesity, physical inactivity, ulcerative colitis, Crohn’s disease, schistosomiasis, polyposis syndrome, family history of colorectal neoplasia and diet
Polyposis syndromes: familial adenomatous polyposis and variants (APC gene), juvenile polyposis (DPC4, PTEN genes), Peutz-Jeghers syndrome (STK11 gene) and Lynch syndrome and variants (MSH2, MLH1, PMS1, PMS2, MSH3 and MSH6 genes)
Diet risk factors: low vegetable fiber, high refined carbohydrates, increased beef consumption and decreased Vitamins A, C, E; low fiber prolongs transit time (toxic oxidative byproducts are in longer contact with colonic mucosa) and alters bacterial flora; beef consumption enhances synthesis of bile acids by liver, which may be converted into carcinogens by bile acids
Screening: endoscopy, guaiac stool examination; serum CEA (elevated levels associated with various carcinomas or liver disease, useful for monitoring recurrences but not sensitive for early tumors)
Symptoms: Left sided carcinomas: rectal bleeding, change in bowel habits (alternating diarrhea and constipation)
Right sided carcinomas: anemia due to blood loss, vague abdominal pain; cecal tumors may mimic appendicitis
Metastases: most commonly to regional lymph nodes and liver; also peritoneum, lung and ovaries; metastases may simulate primary tumors of affected organs
Prognosis: 5 year survival 40-60%; most recurrences are within 2 years

Prognostic factors
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Poor prognostic factors:
● High stage (depth of invasion)
● Positive radial margins (particularly rectal carcinoma)
● High grade / poorly differentiated tumors
● Small cell, mucinous, anaplastic or signet ring subtypes
● Flat or ulcerative carcinomas tend to invade deeper (and have higher stage) than polypoid carcinomas (depth of invasion in a polyp – Haggitt level has prognostic significance, Gastroenterology 1985;89:328)
● Also highly infiltrative growth pattern at margin, extensive tumor budding and undifferentiated cells (seen more commonly in right sided tumors)
● Free tumor cells in peritoneal space (Am J Clin Pathol 2003;119:108), angiolymphatic invasion (particularly outside of bowel wall)
● Perineurial invasion, very young or very old patients; male patients
● Perforation
● Elevated serum CEA > 5 ng/ml, reduced claudin 1 expression in Stage II tumors (Mod Pathol 2005;18:511)
● HER-2/neu and VEGF are not important prognostic markers of colon cancer (BMC Cancer 2011;11:277)

Treatment
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● Resection with endoscopic follow up
● Local excision for small rectal carcinomas
● Endoscopic mucosal resection for superficial (intramucosal) carcinomas
● Surgical excision of isolated distant metastases
● Radiation therapy or chemotherapy

Additional references
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Wikipedia

End of Colon tumor > Carcinoma > General of colon


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