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Colon Cancer
Colorectal Cancer
PATHOPHYSIOLOGY
Most arise from adenomas (adenocarcinoma), when polyps invade the submucosa or deeper layers.
Thus, they follow the classic adenocarcinoma pathway, in which mutations accumulate over 10-15 years and facilitate progression from adenoma to carcinoma.
Serrated pathway carcinomas, on the other hand, are associated with mutations in BRAF or KRAS genes and hypermethylation.
RISK FACTORS
Adenomatous polyps, age (over 50 is higher risk), inflammatory bowel disease, and family history.
SIGNS & SYMPTOMS
Blood in the stool, abdominal pain, and iron deficiency anemia.
SCREENING & DIAGNOSIS
Screening should begin at age 45, or earlier if a patient has family members with colorectal cancer, or if there is an expectation of early onset.
Diagnosis: We use colonoscopy or flexible sigmoidoscopy to diagnose cancer.
See example of colorectal cancer
For staging, we can use CT scans and physical exams to look for metastasis. The liver is the most common site for distant metastasis in colorectal cancer.
TREATMENT
Treatment involves surgical resection; adjuvant chemotherapy and radiation may be recommended.
Unfortunately, recurrence of colorectal cancer is common, especially cancers of the rectum.
HEREDITARY COLON CANCERS
Lynch Syndrome, aka, Hereditary Nonpolyposis CRC is the most common cause of hereditary colorectal cancer.
It is the result of mismatch repair and microsatellite instability cancer pathways.
Lynch syndrome is associated with early cancer onset, and patients are more likely to develop other cancers, especially of the endometrium, liver, and brain.